Question

i like to know how i have to use radio button CheckedChanged property when the radio button there is in gridview and this gridview itself is inside of 1 user control and user control is inside of detail view control.

before i have learned how i have to find radio button control in another control. but after finding i do not know how to make CheckedChanged property for that?

protected void btnShowAddTransmittaltoCon_Click(object sender, EventArgs e)
{
    Transmittallistfortest transmittalList = (Transmittallistfortest)DetailsView1.FindControl("Transmittallistfortest1");
    GridView g3 = transmittalList.FindControl("GridViewTtransmittals") as GridView;
    foreach (GridViewRow di in g3.Rows)

    {

        RadioButton rad = (RadioButton)di.FindControl("RadioButton1");
        //Giving Error:Object reference not set to an instance of an object.
        if (rad != null && rad.Checked)
        {
            var w = di.RowIndex;

            Label1.Text = di.Cells[1].Text;
        }

Answer 1

Replace this

RadioButton rad = (RadioButton)di.FindControl("RadioButton1");

with this:

RadioButton rad = di.FindControl("RadioButton1") as RadioButton;

You won’t get an exception but it may return NULL – in which case it’ll be caught in the ifstatement: rad != null.

The whole point of using the as keyword is this:

as => won’t throw an exception – it just reports null.

---

By the way: You should retrieve the RadioButton this way:

if(di.RowType == DataControlRowType.DataRow)
{
    RadioButton rad = di.FindControl("RadioButton1") as RadioButton;
}

To define the CheckedChange event, do this:

//rad.Checked = true;

rad.CheckedChanged += new EventHandler(MyCheckedChangeEventHandler);

Then define the handler:

protected void MyCheckedChangeEventHandler)(object sender, EventArgs e)
{
    RadioButton rb = (RadioButton)sender;

    if (rb.Checked)
    {
        // Your logic here...
    }
}