[sqlite] Reading Blob to file in C#

[Seysan]

YOU ARE  a LIFE SAVER man!

it worked!

Thank you so very much!
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[sqlite] Reading Blob to file in C#

[Seysan]

Hello,

I've asked this question on Ssystem.Data.SQlite Forum, and after 2
days not even 1 Reply !

How can I read a blob column in C#?

I have tried 4 different ways, so far no success.

Does anyone have any sample code? or at least any documentation on this ???
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[sqlite] sqlite Exception System.InvalidCastException: Specified cast is not valid.

[Seysan]

This is the Code in C#:

SQLiteDataReader rdr;
SQLiteCommand contentCommand;
String cmd = String.Format("SELECT
filename,content,filesize FROM documents WHERE did={0}",did);

contentCommand = sqlconn.CreateCommand();
contentCommand.CommandText = cmd;
rdr = contentCommand.ExecuteReader();
rdr.Read();
MessageBox.Show(rdr.GetFieldType(1).ToString());
MessageBox.Show(rdr.FieldCount.ToString());

-->long len = rdr.GetBytes(1, 0, null, 0, 0);
Byte[] buf = new Byte[len];
rdr.GetBytes(1, 0, buf, 0,(int) len);

I get the Exception there!  sqlite Exception
System.InvalidCastException: Specified cast is not valid.

The GetFieldType Shows: Systes.Byte[]

What is it that I'm doing wrong?
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[sqlite] Reading Blob/Writing to File in C# 2008

[Seysan]

I still have that problem.

can anyone help me in right direction?
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[sqlite] Reading Blob/Writing to File in C# 2008

[Seysan]

When I used your code I get:  No current row

If I use: rdr.Read();
before your code, I get the same exception as before.
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[sqlite] Reading Blob/Writing to File in C# 2008

[Seysan]

Hello,
I'm Using  "System.Data.SQLite" in VS 2008 C#.

I'm using DataReader to read the data.
Everything works find except the BLOB.
I want to get that Blob and Write it to a File.

Blob data is mostly Picture and Music.

Here a bit of Code:
did-> is the document id.

String cmd = String.Format("SELECT filename,content FROM documents
WHERE did={0}",did);

   contentCommand = sqlconn.CreateCommand();
   contentCommand.CommandText = cmd;
   rdr = contentCommand.ExecuteReader();

I tried rdr.GetBytes but it give me this Error:

System.InvalidCastException was unhandled
 Message="Specified cast is not valid."
 Source="System.Data.SQLite"
 StackTrace:
  at System.Data.SQLite.SQLiteDataReader.VerifyType(Int32 i, DbType typ)
  at System.Data.SQLite.SQLiteDataReader.GetBytes(Int32 i, Int64
fieldOffset, Byte[] buffer, Int32 bufferoffset, Int32 length)
  at SDA_Viewer.Form1.btnShow_Click(Object sender, EventArgs e)
in Form1.cs:line 139
  at System.Windows.Forms.Control.OnClick(EventArgs e)
  at System.Windows.Forms.Button.OnClick(EventArgs e)
  at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
  at System.Windows.Forms.Control.WmMouseUp(Message& m,
MouseButtons button, Int32 clicks)
  at System.Windows.Forms.Control.WndProc(Message& m)
  at System.Windows.Forms.ButtonBase.WndProc(Message& m)
  at System.Windows.Forms.Button.WndProc(Message& m)
  at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&
m)
  at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&
m)
  at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr
hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
  at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
  at
System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32
dwComponentID, Int32 reason, Int32 pvLoopData)
  at
System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32
reason, ApplicationContext context)
  at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32
reason, ApplicationContext context)


I've read most of the mailing list archive, and any other resource on
Web, So far nothing !

Please Help,
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