I hava a table AVUKAT Posts--> HESAP, MUSTERI, AVUKAT

This really is my remove button code

protected void Delete_Click(object sender, EventArgs e)
        {
            string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;

            SqlConnection myConnection = new SqlConnection(strConnectionString);
            myConnection.Open();


            string hesap = Label1.Text;
            string musteriadi = DropDownList1.SelectedItem.Value;
            string avukat = DropDownList2.SelectedItem.Value;

            SqlCommand cmd = new SqlCommand("DELETE FROM AVUKAT WHERE (@HESAP, @MUSTERI, @AVUKAT)", myConnection);

            cmd.Parameters.AddWithValue("@HESAP", hesap);
            cmd.Parameters.AddWithValue("@MUSTERI", musteriadi);
            cmd.Parameters.AddWithValue("@AVUKAT", avukat);
            cmd.Connection = myConnection;

            SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            Grid_Goster.DataSource = dr;
            Grid_Goster.Visible = true;
            myConnection.Close();
        }

However it creates a mistake such as this.

Server Error in '/' Application.
An expression of non-boolean type specified in a context where a condition is expected, near ','.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Data.SqlClient.SqlException: An expression of non-boolean type specified in a context where a condition is expected, near ','.
Source Error:
Line 83:             cmd.Connection = myConnection;
Line 84: 
Line 85:             SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
Line 86:             Grid_Goster.DataSource = dr;
Line 87:             Grid_Goster.Visible = true;

I can not discover the error.. Where's?

Your sql command presently is DELETE FROM AVUKAT WHERE (@HESAP, @MUSTERI, @AVUKAT)

This must be transformed to become a valid Remove command in line with the actual table. According to that which you authored above, it will have to be:

DELETE FROM AVUKAT 
WHERE HESAP = @HESAP AND 
      MUSTERI = @MUSTERI AND 
      AVUKAT = @AVUKAT

Your SQL is wrong, you have not given a boolean condition to specify which rows ought to be erased.

Should you desired to remove according to all individuals parameters being true:

DELETE FROM AVUKAT 
WHERE HESAP = @HESAP
AND MUSTERI = @MUSTERI 
AND AVUKAT = @AVUKAT

Or maybe you desired to remove according to any kind of individuals parameters being true:

DELETE FROM AVUKAT 
WHERE HESAP = @HESAP
OR MUSTERI = @MUSTERI 
OR AVUKAT = @AVUKAT

You have to provide boolean expressions inside your SQL statement. For instance:

SqlCommand cmd = new SqlCommand("DELETE FROM AVUKAT WHERE @HESAP = 'foobar' AND @MUSTERI > 0 AND @AVUKAT <> 42")