Sunday, April 11, 2010

Read and Write BLOB Data to a Database

1. Add a table named MyImages to your SQL Server Northwind database. Include the following fields in your table:
          * Identity field that is named "ID" of type Int.
          * Field that is named "Description" of type VarChar with a length of 50.
          * Field that is named "ImgField" of type Image.

   2. Start Visual Studio .NET, and then create a new Visual C# Windows Application project.
   3. Drag two Button controls from the toolbox to the default form, Form1.
   4. In the Properties window, change the Text property of Button1 to Save to Database (from File), and then change the Text property of Button2 to Save to File (from Database).
   5. Add the following code to the top of the Code window:

      using System.Data;
      using System.Data.SqlClient;
      using System.IO;
                         

   6. Double-click Button1, and then add the following code to the Button1_Click event handler.

      Note Uid <user name=""> must have permissions to perform these operations on the database.

      {
      SqlConnection con = new SqlConnection("Server=Darkover;uid=<username>;pwd=<b password="">;database=northwind");
      SqlDataAdapter da = new SqlDataAdapter("Select * From MyImages", con);
      SqlCommandBuilder MyCB = new SqlCommandBuilder(da);
      DataSet ds = new DataSet("MyImages");

      da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
      FileStream fs = new FileStream(@"C:\winnt\Gone Fishing.BMP", FileMode.OpenOrCreate, FileAccess.Read);
                 
      byte[] MyData= new byte[fs.Length];
      fs.Read(MyData, 0, System.Convert.ToInt32(fs.Length));
                 
      fs.Close();
                 
      da.Fill(ds,"MyImages");
                     
      DataRow myRow;
      myRow=ds.Tables["MyImages"].NewRow();

      myRow["Description"] = "This would be description text";
      myRow["imgField"] = MyData;
      ds.Tables["MyImages"].Rows.Add(myRow);
      da.Update(ds, "MyImages");

      con.Close();
             
      }
                         

   7. Double-click Button2, and then add the following code to the Button2_Click event handler.

      Note Uid <user name=""> must have permissions to perform these operations on the database.

      {
      SqlConnection con = new SqlConnection("Server=Darkover;uid=<username>;pwd=<b password="">;database=northwind");
      SqlDataAdapter da = new SqlDataAdapter("Select * From MyImages", con);
      SqlCommandBuilder MyCB = new SqlCommandBuilder(da);
      DataSet ds = new DataSet("MyImages");

      byte[] MyData= new byte[0];
                 
      da.Fill(ds, "MyImages");
      DataRow myRow;
      myRow=ds.Tables["MyImages"].Rows[0];
                
      MyData =  (byte[])myRow["imgField"];
      int ArraySize = new int();
      ArraySize = MyData.GetUpperBound(0);

      FileStream fs = new FileStream(@"C:\winnt\Gone Fishing2.BMP", FileMode.OpenOrCreate, FileAccess.Write);
      fs.Write(MyData, 0,ArraySize);
      fs.Close();
      }
                         

   8. Press F5 to compile and to run the application.
   9. Click Save to Database (from File) to load the image, C:\WinNT\Gone Fishing.bmp, into the SQL Server Image field.
  10. Click Save to File (from Database) to save the data from the SQL Server Image field back to a file.

 





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