How to set from textbox's value to datagridview's row number

You can set defaults for the a column by the designer

1. On you DataGridView -> Click Edit Columns
2. Now you should see the Edit Columsn Dialog
3. Select the Column you want to set default
4. Now at the right side you should the property called DataGridViewCellStyle
5. Please click on DataGridViewCellStyle this will show Cell Style Builder Dialog
6. Under Data -> Set the NullValue property to 0.0
7. Keep on clicking Ok Buttons till you are back to the DataGridView

Hope this helps...