null reference with and if statement c#
<p>I am just want to check for empty text boxes and change the text the boxes if they are null in RowEditing event. I just can't figure this out. Of course the some of the boxes will be empty when the Grid is populated. The other question is am I placing this in the right event? </p>

<p>Here is the row editing event :</p>

<pre><code>protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{        
    fill_grid();

    //Set the edit index.
    GridView1.EditIndex = e.NewEditIndex;
    //Bind data to the GridView control.
    check_grid_boxes();
    GridView1.DataBind();
}
</code></pre>

<p>Here is the check_grid_boxes Method : </p>

<pre><code>protected void check_grid_boxes()
{
    if (gtxtLane.Text == "")
    {
        gtxtLane.Text = "0";
    }
    else if (gtxtCarriers.Text == "")
    {
        gtxtCarriers.Text = "0";
    }
    else if (gtxtREV.Text == "")
    { 
        gtxtREV.Text = "0";
    }
    return;
}
</code></pre>

<p>Before you mention Java Script or Jquery. This is a web control and my attempts at using java has not worked. </p>

<p>I changed my code to this : </p>

<pre><code>  protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
        {
            fill_grid();
            GridView1.EditIndex = e.NewEditIndex;

            var lane = (TextBox)GridView1.Rows[e.NewEditIndex].FindControl("gtxtLane");
            var car = (TextBox)GridView1.Rows[e.NewEditIndex].FindControl("gtxtCarriers");
            var badcar = (TextBox)GridView1.Rows[e.NewEditIndex].FindControl("gtxtBadCarriers");

            if (String.IsNullOrEmpty(lane.Text))
            {
                lane.Text = "0";
            }
            else if (String.IsNullOrEmpty(badcar.Text))
            {
                badcar.Text = "0";
            }
            else if (String.IsNullOrEmpty(car.Text))
            {
                car.Text = "0";
            }
               GridView1.DataBind();
         }
</code></pre>
