大型对象BLOB用法代码,CSharp代码库,德仔网

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【CSharp】大型对象BLOB用法
作者:Dezai.CN / 发布于2011/6/22/ 441
<div><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"><summary></span><span style="color: #008000">
</span><span style="color: #808080">///</span><span style="color: #008000"> 从数据库读取Lob到文件
</span><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"></summary></span><span style="color: #808080">
</span><span style="color: #0000ff">private</span><span style="color: #000000"> </span><span style="color: #0000ff">void</span><span style="color: #000000"> ReadLobToFile()
{
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> employeeIdColumn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> employeePhotoColumn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">1</span><span style="color: #000000">;
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferSize </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">100</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] buffer </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[bufferSize];
</span><span style="color: #0000ff">int</span><span style="color: #000000"> byteCountRead;
</span><span style="color: #0000ff">long</span><span style="color: #000000"> currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;

ConnectionStringSettings nwSetting </span><span style="color: #000000">=</span><span style="color: #000000"> ConfigurationManager.ConnectionStrings[</span><span style="color: #800000">"</span><span style="color: #800000">NorthWindDb</span><span style="color: #800000">"</span><span style="color: #000000">];
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlConnection cn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> SqlConnection())
{
cn.ConnectionString </span><span style="color: #000000">=</span><span style="color: #000000"> nwSetting.ConnectionString;
cn.Open();

</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">Select EmployeeID,Photo From Employees</span><span style="color: #800000">"</span><span style="color: #000000">;
</span><span style="color: #008000">/*</span><span style="color: #008000">SequentialAccess 不是加载整行，而是使 DataReader 将数据作为流来加载。
然后可以使用 GetBytes 或 GetChars 方法来指定开始读取操作的字节位置以及正在返回的数据的有限的缓冲区大小。
</span><span style="color: #008000">*/</span><span style="color: #000000">
SqlDataReader rdr </span><span style="color: #000000">=</span><span style="color: #000000"> cmd.ExecuteReader(CommandBehavior.SequentialAccess);
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (rdr.Read())
{
</span><span style="color: #0000ff">int</span><span style="color: #000000"> employeeId </span><span style="color: #000000">=</span><span style="color: #000000"> rdr.GetInt32(employeeIdColumn);
</span><span style="color: #0000ff">string</span><span style="color: #000000"> fileName </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">@"</span><span style="color: #800000">D:\Employee</span><span style="color: #800000">"</span><span style="color: #000000"> </span><span style="color: #000000">+</span><span style="color: #000000"> employeeId.ToString().PadLeft(</span><span style="color: #800080">2</span><span style="color: #000000">, </span><span style="color: #800000">'</span><span style="color: #800000">0</span><span style="color: #800000">'</span><span style="color: #000000">) </span><span style="color: #000000">+</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">.bin</span><span style="color: #800000">"</span><span style="color: #000000">;
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (FileStream fs </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> FileStream(fileName, FileMode.OpenOrCreate, FileAccess.Write))
{
currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #008000">//</span><span style="color: #008000">从指定的列偏移量将字节流读入缓冲区，并将其作为从给定的缓冲区偏移量开始的数组。 </span><span style="color: #008000">
</span><span style="color: #008000">/*</span><span style="color: #008000">
参数
i
类型：Int32 从零开始的列序号。 
dataIndex
类型：Int64 字段中的索引，从其开始读取操作。 
buffer
类型：array<Byte>[]()[] 要将字节流读入的缓冲区。
bufferIndex
类型：Int32 buffer 中写入操作开始位置的索引。 
length
类型：Int32 要复制到缓冲区中的最大长度。 

</span><span style="color: #008000">*/</span><span style="color: #000000">

byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)rdr.GetBytes(employeePhotoColumn, currentIndex, buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, bufferSize);
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (byteCountRead </span><span style="color: #000000">!=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">)
{
fs.Write(buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, byteCountRead);
currentIndex </span><span style="color: #000000">+=</span><span style="color: #000000"> byteCountRead;
byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)rdr.GetBytes(employeePhotoColumn, currentIndex, buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, bufferSize);
}
}
}

}

}
}</span>


<div style="width: 900px" class="cnblogs_code">
<div><!--

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--><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"><summary></span><span style="color: #008000">
</span><span style="color: #808080">///</span><span style="color: #008000"> 得到头信息及图片
</span><span style="color: #808080">///</span><span style="color: #008000"> 该代码检查该照片是否包含OLE头信息。如果包含将从OLE头信息后面开始执行写操作。
</span><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"></summary></span><span style="color: #808080">
</span><span style="color: #0000ff">private</span><span style="color: #000000"> </span><span style="color: #0000ff">void</span><span style="color: #000000"> GetHeadInfo()
{
</span><span style="color: #008000">//</span><span style="color: #008000">OLE头信息大小为78</span><span style="color: #008000">
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> oleOffset </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">78</span><span style="color: #000000">;
</span><span style="color: #008000">//</span><span style="color: #008000">扩展名开始</span><span style="color: #008000">
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> oleTypeStart </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">20</span><span style="color: #000000">;
</span><span style="color: #008000">//</span><span style="color: #008000">扩展名占用长度</span><span style="color: #008000">
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> oleTypeLength </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">12</span><span style="color: #000000">;
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> employeeIdColumn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> employeePhotoColumn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">1</span><span style="color: #000000">;
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferSize </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">100</span><span style="color: #000000">;</span><span style="color: #008000">//</span><span style="color: #008000">must be bigger than oleOffset</span><span style="color: #008000">
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] buffer </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[bufferSize];
</span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferStart </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">int</span><span style="color: #000000"> byteCountRead;
</span><span style="color: #0000ff">long</span><span style="color: #000000"> currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;

ConnectionStringSettings nwSetting </span><span style="color: #000000">=</span><span style="color: #000000"> ConfigurationManager.ConnectionStrings[</span><span style="color: #800000">"</span><span style="color: #800000">NorthWindDb</span><span style="color: #800000">"</span><span style="color: #000000">];
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlConnection cn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> SqlConnection())
{
cn.ConnectionString </span><span style="color: #000000">=</span><span style="color: #000000"> nwSetting.ConnectionString;
cn.Open();
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">Select EmployeeID,Photo From Employees</span><span style="color: #800000">"</span><span style="color: #000000">;
SqlDataReader rdr </span><span style="color: #000000">=</span><span style="color: #000000"> cmd.ExecuteReader(CommandBehavior.SequentialAccess);
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (rdr.Read())
{
</span><span style="color: #0000ff">int</span><span style="color: #000000"> employeeId </span><span style="color: #000000">=</span><span style="color: #000000"> rdr.GetInt32(employeeIdColumn);
</span><span style="color: #008000">//</span><span style="color: #008000">文件路径</span><span style="color: #008000">
</span><span style="color: #0000ff">string</span><span style="color: #000000"> fileName </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">@"</span><span style="color: #800000">D:\Employee\Employee</span><span style="color: #800000">"</span><span style="color: #000000"> </span><span style="color: #000000">+</span><span style="color: #000000"> employeeId.ToString().PadLeft(</span><span style="color: #800080">2</span><span style="color: #000000">, </span><span style="color: #800000">'</span><span style="color: #800000">0</span><span style="color: #800000">'</span><span style="color: #000000">) </span><span style="color: #000000">+</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">.bin</span><span style="color: #800000">"</span><span style="color: #000000">;
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (FileStream fs </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> FileStream(fileName, FileMode.OpenOrCreate, FileAccess.Write))
{
currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (currentIndex </span><span style="color: #000000"><</span><span style="color: #000000"> oleOffset)
{
</span><span style="color: #008000">//</span><span style="color: #008000">第一批次读取</span><span style="color: #008000">
</span><span style="color: #000000">byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)rdr.GetBytes(employeePhotoColumn, currentIndex, buffer,
(</span><span style="color: #0000ff">int</span><span style="color: #000000">)currentIndex, bufferSize </span><span style="color: #000000">-</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)currentIndex);
</span><span style="color: #0000ff">if</span><span style="color: #000000"> (byteCountRead </span><span style="color: #000000">==</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">)
{
</span><span style="color: #0000ff">break</span><span style="color: #000000">;
}
currentIndex </span><span style="color: #000000">+=</span><span style="color: #000000"> byteCountRead;
}
byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)currentIndex;


</span><span style="color: #0000ff">if</span><span style="color: #000000"> (byteCountRead </span><span style="color: #000000">>=</span><span style="color: #000000"> oleOffset)
{
</span><span style="color: #008000">//</span><span style="color: #008000">得到文件类型</span><span style="color: #008000">
</span><span style="color: #0000ff">string</span><span style="color: #000000"> type </span><span style="color: #000000">=</span><span style="color: #000000"> Encoding.ASCII.GetString(buffer, oleTypeStart, oleTypeLength);
</span><span style="color: #0000ff">if</span><span style="color: #000000"> (type </span><span style="color: #000000">==</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">Bitmap Image</span><span style="color: #800000">"</span><span style="color: #000000">)
{
</span><span style="color: #008000">//</span><span style="color: #008000">第一批次,从头信息后开使读取</span><span style="color: #008000">
</span><span style="color: #000000">bufferStart </span><span style="color: #000000">=</span><span style="color: #000000"> oleOffset;
</span><span style="color: #008000">//</span><span style="color: #008000">第一批次的读取大小</span><span style="color: #008000">
</span><span style="color: #000000">byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> byteCountRead </span><span style="color: #000000">-</span><span style="color: #000000"> oleOffset;
}
}

</span><span style="color: #008000">//</span><span style="color: #008000">写入文件</span><span style="color: #008000">
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (byteCountRead </span><span style="color: #000000">!=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">)
{
fs.Write(buffer, bufferStart, byteCountRead);
bufferStart </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
byteCountRead </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">int</span><span style="color: #000000">)rdr.GetBytes(employeePhotoColumn, currentIndex, buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, bufferSize);
currentIndex </span><span style="color: #000000">+=</span><span style="color: #000000"> byteCountRead;
}
}
}
}
}
}</span></div>
</div>


<div style="width: 900px" class="cnblogs_code">
<div><!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
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--><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"><summary></span><span style="color: #008000">
</span><span style="color: #808080">///</span><span style="color: #008000"> 将图片写入到数据库
</span><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"></summary></span><span style="color: #808080">
</span><span style="color: #0000ff">private</span><span style="color: #000000"> </span><span style="color: #0000ff">void</span><span style="color: #000000"> WriteBlobToDb()
{
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferSize </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">100</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] buffer </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[bufferSize];
</span><span style="color: #0000ff">long</span><span style="color: #000000"> currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] photoPtr;

ConnectionStringSettings nwSetting </span><span style="color: #000000">=</span><span style="color: #000000"> ConfigurationManager.ConnectionStrings[</span><span style="color: #800000">"</span><span style="color: #800000">NorthWindDb</span><span style="color: #800000">"</span><span style="color: #000000">];
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlConnection cn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> SqlConnection())
{
cn.ConnectionString </span><span style="color: #000000">=</span><span style="color: #000000"> nwSetting.ConnectionString;
cn.Open();
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">select Textptr(Photo) from employees where employeeID='1'</span><span style="color: #800000">"</span><span style="color: #000000">;
photoPtr </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">byte</span><span style="color: #000000">[])cmd.ExecuteScalar();
}
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">UpdateText employees.Photo @Pointer @Offset null @Data</span><span style="color: #800000">"</span><span style="color: #000000">;
SqlParameter ptrParm </span><span style="color: #000000">=</span><span style="color: #000000"> cmd.Parameters.Add(</span><span style="color: #800000">"</span><span style="color: #800000">Pointer</span><span style="color: #800000">"</span><span style="color: #000000">, SqlDbType.Binary, </span><span style="color: #800080">16</span><span style="color: #000000">);
ptrParm.Value </span><span style="color: #000000">=</span><span style="color: #000000"> photoPtr;
SqlParameter PhotoParm </span><span style="color: #000000">=</span><span style="color: #000000"> cmd.Parameters.Add(</span><span style="color: #800000">"</span><span style="color: #800000">Data</span><span style="color: #800000">"</span><span style="color: #000000">, SqlDbType.Image);
SqlParameter offsetParm </span><span style="color: #000000">=</span><span style="color: #000000"> cmd.Parameters.Add(</span><span style="color: #800000">"</span><span style="color: #800000">Offset</span><span style="color: #800000">"</span><span style="color: #000000">, SqlDbType.Int);
offsetParm.Value </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (FileStream fs </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> FileStream(</span><span style="color: #800000">"</span><span style="color: #800000">Girl.png</span><span style="color: #800000">"</span><span style="color: #000000">, FileMode.Open, FileAccess.Read))
{
</span><span style="color: #0000ff">int</span><span style="color: #000000"> count </span><span style="color: #000000">=</span><span style="color: #000000"> fs.Read(buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, bufferSize);
</span><span style="color: #0000ff">while</span><span style="color: #000000"> (count </span><span style="color: #000000">!=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">)
{
PhotoParm.Value </span><span style="color: #000000">=</span><span style="color: #000000"> buffer;
PhotoParm.Size </span><span style="color: #000000">=</span><span style="color: #000000"> count;
cmd.ExecuteNonQuery();
currentIndex </span><span style="color: #000000">+=</span><span style="color: #000000"> count;
offsetParm.Value </span><span style="color: #000000">=</span><span style="color: #000000"> currentIndex;
count </span><span style="color: #000000">=</span><span style="color: #000000"> fs.Read(buffer, </span><span style="color: #800080">0</span><span style="color: #000000">, bufferSize);
}
}
}
}
MessageBox.Show(</span><span style="color: #800000">"</span><span style="color: #800000">Done</span><span style="color: #800000">"</span><span style="color: #000000">);
}</span></div>
</div>


<div style="width: 900px" class="cnblogs_code">
<div><!--

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--><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"><summary></span><span style="color: #008000">
</span><span style="color: #808080">///</span><span style="color: #008000"> 显示有头信息的图片
</span><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"></summary></span><span style="color: #808080">
</span><span style="color: #0000ff">private</span><span style="color: #000000"> </span><span style="color: #0000ff">void</span><span style="color: #000000"> ShowImgHaveHead()
{
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferSize </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">100</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] buffer </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[bufferSize];
</span><span style="color: #0000ff">long</span><span style="color: #000000"> currentIndex </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">0</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] OleArray;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] photoPtr;

ConnectionStringSettings nwSetting </span><span style="color: #000000">=</span><span style="color: #000000"> ConfigurationManager.ConnectionStrings[</span><span style="color: #800000">"</span><span style="color: #800000">NorthWindDb</span><span style="color: #800000">"</span><span style="color: #000000">];
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlConnection cn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> SqlConnection())
{
cn.ConnectionString </span><span style="color: #000000">=</span><span style="color: #000000"> nwSetting.ConnectionString;
cn.Open();
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">select Photo from employees where employeeID='2'</span><span style="color: #800000">"</span><span style="color: #000000">;
OleArray </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">byte</span><span style="color: #000000">[])cmd.ExecuteScalar();
photoPtr </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[OleArray.Length </span><span style="color: #000000">-</span><span style="color: #000000"> </span><span style="color: #800080">78</span><span style="color: #000000">];
</span><span style="color: #008000">//</span><span style="color: #008000">去除头信息(如此BLob中前78个字节为头信息)</span><span style="color: #008000">
</span><span style="color: #000000">Array.Copy(OleArray, </span><span style="color: #800080">78</span><span style="color: #000000">, photoPtr, </span><span style="color: #800080">0</span><span style="color: #000000">, (OleArray.Length </span><span style="color: #000000">-</span><span style="color: #000000"> </span><span style="color: #800080">78</span><span style="color: #000000">));
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (MemoryStream ms </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> MemoryStream(photoPtr))
{
Bitmap bmp </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> Bitmap(ms);
ptbImg.Image </span><span style="color: #000000">=</span><span style="color: #000000"> bmp;
} 
}

}
MessageBox.Show(</span><span style="color: #800000">"</span><span style="color: #800000">Done</span><span style="color: #800000">"</span><span style="color: #000000">);
}</span></div>
</div>



<div style="width: 900px" class="cnblogs_code">
<div><!--

Code highlighting produced by Actipro CodeHighlighter (freeware)
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--><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"><summary></span><span style="color: #008000">
</span><span style="color: #808080">///</span><span style="color: #008000"> 显示没有头文信息的图片
</span><span style="color: #808080">///</span><span style="color: #008000"> </span><span style="color: #808080"></summary></span><span style="color: #808080">
</span><span style="color: #0000ff">private</span><span style="color: #000000"> </span><span style="color: #0000ff">void</span><span style="color: #000000"> ShowImgNoHead()
{
</span><span style="color: #0000ff">const</span><span style="color: #000000"> </span><span style="color: #0000ff">int</span><span style="color: #000000"> bufferSize </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800080">100</span><span style="color: #000000">;
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] buffer </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> </span><span style="color: #0000ff">byte</span><span style="color: #000000">[bufferSize];
</span><span style="color: #0000ff">byte</span><span style="color: #000000">[] photoPtr;

ConnectionStringSettings nwSetting </span><span style="color: #000000">=</span><span style="color: #000000"> ConfigurationManager.ConnectionStrings[</span><span style="color: #800000">"</span><span style="color: #800000">NorthWindDb</span><span style="color: #800000">"</span><span style="color: #000000">];
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlConnection cn </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> SqlConnection())
{
cn.ConnectionString </span><span style="color: #000000">=</span><span style="color: #000000"> nwSetting.ConnectionString;
cn.Open();
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (SqlCommand cmd </span><span style="color: #000000">=</span><span style="color: #000000"> cn.CreateCommand())
{
cmd.CommandText </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #800000">"</span><span style="color: #800000">select Photo from employees where employeeID='2'</span><span style="color: #800000">"</span><span style="color: #000000">;
photoPtr </span><span style="color: #000000">=</span><span style="color: #000000"> (</span><span style="color: #0000ff">byte</span><span style="color: #000000">[])cmd.ExecuteScalar();
</span><span style="color: #0000ff">using</span><span style="color: #000000"> (MemoryStream ms </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> MemoryStream(photoPtr))
{
Bitmap bmp </span><span style="color: #000000">=</span><span style="color: #000000"> </span><span style="color: #0000ff">new</span><span style="color: #000000"> Bitmap(ms);
ptbImg.Image </span><span style="color: #000000">=</span><span style="color: #000000"> bmp;
} 
} 
}
MessageBox.Show(</span><span style="color: #800000">"</span><span style="color: #800000">Done</span><span style="color: #800000">"</span><span style="color: #000000">);
}</span></div>
</div>
</div>
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