// Click event for the button labeled SqlBlob2File.
SqlChunkBlob2File(destfilepath);
// Click event for the button labeled OLDbBlob2File.
OlDbChunkBlob2File(destfilepath);
// Click event for the button labeled File2OleDbBlob.
ChunkFile2OleDbBlob(sourcefilepath);
//Click event for the button labeled File2SqlBlob.
ChunkFile2SqlBlob(sourcefilepath);
在 Form1 中貼上下列四個函式:
public void SqlChunkBlob2File(string DestFilePath)
{
try
{
int PictureCol = 0; // position of Picture column in DataReader
int BUFFER_LENGTH = 32768; // chunk size
SqlConnection cn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;");
// Make sure Photo is non-NULL and return TEXTPTR to it.
SqlCommand cmdGetPointer = new SqlCommand("SELECT @Pointer=TEXTPTR(Picture), @Length=DataLength(Picture) FROM Categories WHERE CategoryName='Test'", cn);
SqlParameter PointerOutParam = cmdGetPointer.Parameters.Add("@Pointer", SqlDbType.VarBinary, 100);
PointerOutParam.Direction = ParameterDirection.Output;
SqlParameter LengthOutParam = cmdGetPointer.Parameters.Add("@Length", SqlDbType.Int);
LengthOutParam.Direction = ParameterDirection.Output;
cn.Open();
cmdGetPointer.ExecuteNonQuery();
if(PointerOutParam.Value == null)
{
cn.Close();
// Add code to handle NULL BLOB.
return;
}
// Set up READTEXT command, parameters, and open BinaryReader.
SqlCommand cmdReadBinary = new SqlCommand("READTEXT Categories.Picture @Pointer @Offset @Size HOLDLOCK", cn);
SqlParameter PointerParam = cmdReadBinary.Parameters.Add("@Pointer", SqlDbType.Binary, 16);
SqlParameter OffsetParam = cmdReadBinary.Parameters.Add("@Offset", SqlDbType.Int);
SqlParameter SizeParam = cmdReadBinary.Parameters.Add("@Size", SqlDbType.Int);
SqlDataReader dr;
System.IO.FileStream fs = new System.IO.FileStream(DestFilePath, System.IO.FileMode.Create, System.IO.FileAccess.Write);
int Offset= 0;
OffsetParam.Value = Offset;
Byte []Buffer = new Byte[BUFFER_LENGTH ];
// Read buffer full of data and write to the file stream.
do
{
PointerParam.Value = PointerOutParam.Value;
// Calculate buffer size - may be less than BUFFER_LENGTH for last block.
if( (Offset + BUFFER_LENGTH) >= System.Convert.ToInt32(LengthOutParam.Value))
SizeParam.Value = System.Convert.ToInt32(LengthOutParam.Value) - Offset;
else SizeParam.Value = BUFFER_LENGTH;
dr = cmdReadBinary.ExecuteReader(CommandBehavior.SingleResult);
dr.Read();
dr.GetBytes(PictureCol, 0, Buffer, 0, System.Convert.ToInt32(SizeParam.Value));
dr.Close();
fs.Write(Buffer, 0, System.Convert.ToInt32(SizeParam.Value));
Offset += System.Convert.ToInt32(SizeParam.Value);
OffsetParam.Value = Offset;
}while(Offset < System.Convert.ToInt32(LengthOutParam.Value));
fs.Close();
cn.Close();
}
catch(SqlException ex)
{
MessageBox.Show (ex.Message);
}
}
public void OleDbChunkBlob2File(string DestFilePath)
{
try
{
int PictureCol= 0; // Position of picture column in DataReader.
int BUFFER_LENGTH = 32768;// Chunk size.
OleDbConnection cn = new OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;");
// Make sure Photo is non-NULL and return TEXTPTR to it.
OleDbCommand cmdGetPointer = new OleDbCommand("SELECT ?=TEXTPTR(Picture), ?=DataLength(Picture) FROM Categories WHERE CategoryName='Test'", cn);
OleDbParameter PointerOutParam = cmdGetPointer.Parameters.Add("@Pointer", OleDbType.VarBinary, 100);
PointerOutParam.Direction = ParameterDirection.Output;
OleDbParameter LengthOutParam = cmdGetPointer.Parameters.Add("@Length", OleDbType.Integer);
LengthOutParam.Direction = ParameterDirection.Output;
cn.Open();
cmdGetPointer.ExecuteNonQuery();
if(PointerOutParam.Value == DBNull.Value )
{
cn.Close();
// Add code to deal with NULL BLOB.
return;
}
// Set up READTEXT command, parameters, and open BinaryReader.
OleDbCommand cmdReadBinary = new OleDbCommand("READTEXT Categories.Picture ? ? ? HOLDLOCK", cn);
OleDbParameter PointerParam = cmdReadBinary.Parameters.Add("@Pointer", OleDbType.Binary, 16);
OleDbParameter OffsetParam = cmdReadBinary.Parameters.Add("@Offset", OleDbType.Integer);
OleDbParameter SizeParam = cmdReadBinary.Parameters.Add("@Size", OleDbType.Integer);
OleDbDataReader dr;
System.IO.FileStream fs = new System.IO.FileStream(DestFilePath, System.IO.FileMode.Create, System.IO.FileAccess.Write);
int Offset= 0;
OffsetParam.Value = Offset;
Byte[] Buffer = new Byte[BUFFER_LENGTH];
//Read buffer full of data and write to the file stream.
do
{
PointerParam.Value = PointerOutParam.Value;
// Calculate buffer size - may be less than BUFFER_LENGTH for last block.
if((Offset + BUFFER_LENGTH) >= System.Convert.ToInt32(LengthOutParam.Value))
SizeParam.Value = System.Convert.ToInt32(LengthOutParam.Value) - Offset;
else SizeParam.Value = BUFFER_LENGTH;
dr = cmdReadBinary.ExecuteReader(CommandBehavior.SingleResult);
dr.Read();
dr.GetBytes(PictureCol, 0, Buffer, 0, System.Convert.ToInt32(SizeParam.Value));
dr.Close();
fs.Write(Buffer, 0, System.Convert.ToInt32(SizeParam.Value));
Offset += System.Convert.ToInt32(SizeParam.Value);
OffsetParam.Value = Offset;
}while( Offset < System.Convert.ToInt32(LengthOutParam.Value));
fs.Close();
cn.Close();
}
catch(OleDbException ex)
{
MessageBox.Show (ex.Message);
}
}
按下 F5 以執行程式碼，然後按一下 [File2OleDbBlob 以確定您嘗試將寫出至磁碟上的.bmp 檔案之前，載入 SQL Server 資料庫中的圖像。
重要：本文是以 Microsoft 機器翻譯軟體翻譯而成，而非使用人工翻譯而成。Microsoft 同時提供使用者人工翻譯及機器翻譯兩個版本的文章，讓使用者可以依其使用語言使用知識庫中的所有文章。但是，機器翻譯的文章可能不盡完美。這些文章中也可能出現拼字、語意或文法上的錯誤，就像外國人在使用本國語言時可能發生的錯誤。Microsoft 不為內容的翻譯錯誤或客戶對該內容的使用所產生的任何錯誤或損害負責。Microsoft也同時將不斷地就機器翻譯軟體進行更新。
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