VB.Net The variable name '@srno' has already been declared. variable names must be unique within a query batch or stored procedure.

Hi nirmal90,

This error is due to passing null value to parameter. you must check parameter for null value. If it is null you must pass DBNull.Value

and you are missing @ symbol while passing the parameters to the command object.

If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(1).Value) Then
    cmd.Parameters.AddWithValue("@ItemCode", DataGridView1.Rows(i).Cells(1).Value)
Else
    cmd.Parameters.AddWithValue("@ItemCode", DBNull.Value)
End If

Check with the below code.

    If con.State = ConnectionState.Open Then
        con.Close()
    End If
    Dim i As Integer
    Dim rs1 As String
    Try
        For i = 0 To DataGridView1.Rows.Count - 1
            rs1 = "INSERT INTO tblProductsve(srno,ItemCode, ProDes, Price,Qty,amt,subtot) VALUES(@srno,@ItemCode, @ProDes, @Price,@Qty,@amt,@subtot)"

            Dim cmd As New SqlClient.SqlCommand(rs1, con)

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(0).Value) Then
                cmd.Parameters.AddWithValue("@srno", DataGridView1.Rows(i).Cells(0).Value)
            Else
                cmd.Parameters.AddWithValue("@srno", DBNull.Value)
            End If

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(1).Value) Then
                cmd.Parameters.AddWithValue("@ItemCode", DataGridView1.Rows(i).Cells(1).Value)
            Else
                cmd.Parameters.AddWithValue("@ItemCode", DBNull.Value)
            End If

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(2).Value) Then
                cmd.Parameters.AddWithValue("@ProDes", DataGridView1.Rows(i).Cells(2).Value)
            Else
                cmd.Parameters.AddWithValue("@ProDes", DBNull.Value)
            End If

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(3).Value) Then
                cmd.Parameters.AddWithValue("@Price", DataGridView1.Rows(i).Cells(3).Value)
            Else
                cmd.Parameters.AddWithValue("@Price", DBNull.Value)

            End If

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(4).Value) Then
                cmd.Parameters.AddWithValue("@Qty", DataGridView1.Rows(i).Cells(4).Value)
            Else
                cmd.Parameters.AddWithValue("@Qty", DBNull.Value)
            End If

            If Not String.IsNullOrEmpty(DataGridView1.Rows(i).Cells(5).Value) Then
                cmd.Parameters.AddWithValue("@amt", DataGridView1.Rows(i).Cells(5).Value)
            Else
                cmd.Parameters.AddWithValue("@amt", DBNull.Value)
            End If

            If Not String.IsNullOrEmpty(TextBox1.Text) Then
                cmd.Parameters.AddWithValue("@subtot", TextBox1.Text)
            Else
                cmd.Parameters.AddWithValue("@subtot", DBNull.Value)
            End If
            con.Open()

            cmd.ExecuteNonQuery()

            con.Close()

        Next

        MessageBox.Show("Save Successully ")

    Catch ex As Exception
        MsgBox(ex.Message)

    End Try