在C#/SQL 2005中读取BLOB数据的有效内存方法

article here 还是这个 blog post 关于如何做的详细解释。

基本上,您需要使用SqlDataReader并指定 SequentialAccess

基本上是这样的:

SqlDataReader myReader = getEmp.ExecuteReader(CommandBehavior.SequentialAccess);

while (myReader.Read())
{
   int startIndex = 0;

   // Read the bytes into outbyte[] and retain the number of bytes returned.
   retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

   // Continue reading and writing while there are bytes beyond the size of the buffer.
   while (retval == bufferSize)
   {
      // write the buffer to the output, e.g. a file
      ....

      // Reposition the start index to the end of the last buffer and fill the buffer.
      startIndex += bufferSize;
      retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
   }

   // write the last buffer to the output, e.g. a file
   ....
}

// Close the reader and the connection.
myReader.Close();

马克

IDataReader Here's a version for CLOBs -斑点实际上是相同的,但有一个 byte[] 和 GetBytes(...)

比如:

using (var reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
    byte[] buffer = new byte[8040]; // or some multiple (sql server page size)
    while (reader.Read()) // each row
    {
        long dataOffset = 0, read;
        while ((read = reader.GetBytes(
            colIndex, dataOffset, buffer, 0, buffer.Length)) > 0)
        {
            // TODO: process "read"-many bytes from "buffer"
            dataOffset += read;
        }
    }
}