Represents a variable-length stream of binary data to be stored in or retrieved from a database.
In this example two functions are presented. First can upload a file onto a server, and second can retrieve a BLOB field and paste it into a file. Notice that two classes used here (BinaryWriter and BinaryReader) to provide more flexible stream manipulation are actually redundant for simple data transfer operations.
public void DownloadBlob(MySqlConnection myConnection)
{
MySqlCommand myCommand = new MySqlCommand("SELECT * FROM Test.Pictures", myConnection);
myConnection.Open();
MySqlDataReader myReader = myCommand.ExecuteReader(System.Data.CommandBehavior.Default);
try
{
while (myReader.Read())
{
MySqlBlob myBlob = myReader.GetMySqlBlob(myReader.GetOrdinal("Picture"));
if(!myBlob.IsNull)
{
string FN = myReader.GetString(myReader.GetOrdinal("PicName"));
FileStream fs = new FileStream("D:\\Tmp\\"+FN+".bmp", FileMode.Create);
BinaryWriter w = new BinaryWriter(fs);
w.Write(myBlob.Value);
w.Close();
fs.Close();
Console.WriteLine(FN+" downloaded.");
}
}
}
finally
{
myReader.Close();
myConnection.Close();
}
}
public void UploadBlob(MySqlConnection myConnection)
{
FileStream fs = new FileStream("D:\\Tmp\\_Water.bmp", FileMode.Open, FileAccess.Read);
BinaryReader r = new BinaryReader(fs);
MySqlBlob myBlob = new MySqlBlob(r.ReadBytes((int)fs.Length));
MySqlCommand myCommand = new MySqlCommand("INSERT INTO Test.Pictures (ID, PicName, Picture) VALUES(1,'Water',:Pictures)", myConnection);
myCommand.Parameters.Add("Pictures",myBlob);
myConnection.Open();
try
{
Console.WriteLine(myCommand.ExecuteNonQuery()+" rows affected.");
}
finally
{
myConnection.Close();
r.Close();
}
}
Public Sub DownloadBlob(ByVal myConnection As MySqlConnection)
Dim myCommand As New MySqlCommand("SELECT * FROM Test.Pictures", myConnection)
myConnection.Open()
Dim myReader As MySqlDataReader = myCommand.ExecuteReader(System.Data.CommandBehavior.Default)
Try
While myReader.Read()
Dim myBlob As MySqlBlob = myReader.GetMySqlBlob(myReader.GetOrdinal("Picture"))
If Not myBlob.IsNull Then
Dim FN As String = myReader.GetString(myReader.GetOrdinal("PicName"))
Dim fs As FileStream = New FileStream("D:\Tmp\" + FN + ".bmp", FileMode.Create)
Dim w As BinaryWriter = New BinaryWriter(fs)
w.Write(myBlob.Value)
w.Close()
fs.Close()
Console.WriteLine(String.Concat(FN, " downloaded."))
End If
End While
Finally
myReader.Close()
myConnection.Close()
End Try
End Sub
Public Sub UploadBlob(ByVal myConnection As MySqlConnection)
Dim fs As FileStream = New FileStream("D:\Tmp\_Water.bmp", FileMode.Open, FileAccess.Read)
Dim r As BinaryReader = New BinaryReader(fs)
Dim myBlob As MySqlBlob = New MySqlBlob(r.ReadBytes(Convert.ToInt32(fs.Length)))
Dim myCommand As MySqlCommand = New MySqlCommand("INSERT INTO Test.Pictures (ID, PicName, Picture) VALUES(2,'Water',:Pictures)", myConnection)
myCommand.Parameters.Add("Pictures", myBlob)
myConnection.Open()
Try
Console.WriteLine(String.Concat(myCommand.ExecuteNonQuery(), " rows affected."))
Finally
myConnection.Close()
r.Close()
End Try
End Sub
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2