How to generate a sum of a particular column in DataGridView with C#?

[Sean Len]

Hi guys, currently Im working on a program where generate a datagridview from database.
After generating the datagridview, i would like to add another row below the column to sum the value.

Example:
Original DataGridView
----------------------
|ID | Name | Value |
----------------------
| 1| User1| 2000|
| 2| User2| 1500|
| 3| User3| 500|
----------------------

Then I would like to add another row to display to sum:
----------------------
|ID | Name | Value |
----------------------
| 1| User1| 2000|
| 2| User2| 1500|
| 3| User3| 500|
| | | 4000|
----------------------

How should I targeting the "Value" Column?
I perform alot of research online and I manage to get generate all column with Int32 Data Type.

public Form1()
        {
            InitializeComponent();
            this.dataGridView1.CellPainting += new DataGridViewCellPaintingEventHandler(dataGridView1_CellPainting);
        }
        void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            int sum = 0;
            // only draw the cells of the extra row by ourselves, leaving the rest cells to the system
            if (e.RowIndex == this.dataGridView1.NewRowIndex && e.ColumnIndex > -1)
            {
                for (int i = 0; i < this.dataGridView1.NewRowIndex; i++)
                {
                    if (this.dataGridView1.Rows[i].Cells[e.ColumnIndex].Value.ToString().Trim() != "" &&
                        this.dataGridView1.Rows[i].Cells[e.ColumnIndex].ValueType.Name == "Int32")
                    {
                        sum += (int)this.dataGridView1.Rows[i].Cells[e.ColumnIndex].Value;
                    }
                }
                e.PaintBackground(e.CellBounds, false);
                e.Graphics.DrawString(sum.ToString(), this.dataGridView1.Font, Brushes.Black, e.CellBounds.Left + 2, e.CellBounds.Top + 2);

                e.Handled = true;
            }
        }

But when I try to target only 1 particualr column it give me error.

Anyone could help me with this?

Thanks!

[Sfreak]

You can perform a loop like:

int sum = 0;
for (int x = 0; x < dataGridView1.Rows.Count; x++ )
{
  sum += Convert.ToInt32(dataGridView1.Rows[x].Cells["Column"].Value);
}