if (row.Cells[2].Text.ToString() == " ")
            {
                txtstreet.Text = string.Empty;
            }

Help me out pls. I want to check row.cell[2].Text for null

In my suggestion, you can put label to cell and fill, then check label is empty or not.

Why can't you do the following?

if (row.Cells[2].Text == null || row.Cells[2].Text.ToString() == " ")
{
    txtstreet.Text = string.Empty;
}

//--- myCell is a Cell object

if (myCell.Value == null && myCell.Formula == "")
{
//--- Cell is empty
}

windso0, myCell.Formula? Where are you getting this property from?

Thanks dudes for nice suggestion but my problem is still there i have a dropdownlist which is populated from Province table.In GridView SelectedIndexChanging When i select the row then it fill all the texboxes and dropdownlist.Problm is that if in Province field is null then it throws exception.
Exception:
'ddlstate' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value.
On Populating DrodownList i use this approch.
ddlstate.Items.Insert(0, "--Select Province--");
GridView Code SelectedIndexChanging

if (row.Cells[9].Text == null || row.Cells[9].Text.ToString() == " ")
                
            {
                ddlstate.SelectedIndex = -1;
            }
            else
            {
                ddlstate.SelectedValue = row.Cells[9].Text;
            }

The value property and the text property are 2 different things. Are you sure you don't need to actually get the Text and not the Value?

ddlstate.Items.FindByText(row.Cells[9].Text).Selected;

Dude that line of code gives error
ddlstate.Items.FindByText(row.Cells[9].Text).Selected;
Error 1 Only assignment, call, increment, decrement, and new object expressions can be used as a statement.

Sorry, I forgot to complete your code. You realize that Intellesnse tells you what are properties and what are methods in the list that comes up right?

ddlstate.Items.FindByText(row.Cells[9].Text).Selected = true;