How to find id using hiddenfield in gridview on button click

Question

My update button is outside gridview

 

I am trying but its showing error "Object reference not set to an instance of an object." on "string strhfId = (gvRow.FindControl("hfId") as HiddenField).Value;"

 

I have tried different too

 

HiddenField hfId = (HiddenField)gridData.SelectedRow.Cells[0].FindControl("hfId");

 

but error is same

 

protected void lnkUpdate_Click(object sender, EventArgs e)

{

//HiddenField hfId = (HiddenField)gridData.SelectedRow.Cells[0].FindControl("hfId");   // Error is here

//HiddenField strId = ((HiddenField)gridData.Rows[0].FindControl("hfIdValue"));

//String value = strId.Value;

LinkButton btn = sender as LinkButton;

GridViewRow gvRow = btn.NamingContainer as GridViewRow;

string strhfId = (gvRow.FindControl("hfId") as HiddenField).Value;  // Error is here

try

{

//HiddenField hfIdc = (HiddenField)gridData.SelectedRow.Cells[0].FindControl("hfIdValue");

List parameters = new List

{

};

parameters.Add(new SqlParameter("@P_APPLICATION_ID", strhfId));

parameters.Add(new SqlParameter("@P_APPLICATION_NAME", txtApplicationName.Text));

parameters.Add(new SqlParameter("@P_MODE", "E"));

string strResponse = objAppFunctionModule.ExecuteNonQueryMethod(strUSP_APPLICATION_MST, parameters);

PopulateGrid();

}

catch (Exception ex)

{

lblResponse.Text = ex.Message;

}

}