null引用with和if语句c＃

Question

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?

Here is the row editing event :

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();
}

Here is the check_grid_boxes Method :

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;
}

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

I changed my code to this :

  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();
         }

Answer 1

You must get a reference to the TextBoxes that are inside that row being edited like this:

GridView1.EditIndex = e.NewEditIndex;

TextBox gtxtLane = (TextBox)GridView1.Rows[e.NewEditIndex].FindControl("gtxtLane");

Answer 2

DUH!!!! how bout --> select isnull(lane,'0') as Lane <---. I can't believe I didn't think of that!! 6 hours wasted!!

Answer 3

You could use the nulldisplaytext property of the gridview

<asp:boundfield datafield="discounttype"
            nulldisplaytext="0"
            headertext="Discount Type"/>

Answer 4

I'm guessing you're getting a reference problem, because the compiler doesn't know where to get gtxtLane and the rest from. Remember that each row in the grid has its own version of these controls, so you will need to reference them directly. You can use FindControl on the row object. You can get a reference for the row object from GridViewEditEventArgs . Your code will look something like this ( e refers to GridViewEditEventArgs )

var gtxtLane = (TextBox)GridView1.Rows[e.NewEditIndex].FindControl("gtxtLane");
if (gtxtLane.Text == "")
{
    gtxtLane.Text = "0";
}

e.NewEditIndex gets you the index of the row being edited, we use that to get the row object from the gridview, then we find the wanted control, and cast it to TextBox , then use it. Rinse and repeat.