asp.net textbox not updated from another task - asp.net

Question

I have a GridView and on its SelectedIndexChanged the code is fired:
protected void grdEntry_SelectedIndexChanged(object sender, EventArgs e)
{
lblAssignId.Text = grdEntry.SelectedRow.Cells[1].Text == " "
? ""
: grdEntry.SelectedRow.Cells[1].Text;
Ob.BranchId = Globals.BranchID;
Ob.AssignId = lblAssignId.Text;
DataSet dsMain = GetAssignDetails(Ob);
if (dsMain.Tables[0].Rows.Count != 0)
{
// some other code
Task.Factory.StartNew(() => FillMemberShipAndBarCode(dsMain.Tables[0].Rows[0]["CustomerCode"].ToString(), Ob.BranchId));
}
}
and the code for filling membership id is
private void FillMemberShipAndBarCode(string customerCode, string branchId)
{
var sqlCommand = new SqlCommand
{
CommandText = "sp_customermaster",
CommandType = CommandType.StoredProcedure
};
sqlCommand.Parameters.AddWithValue("#CustomerCode", customerCode);
sqlCommand.Parameters.AddWithValue("#BranchId", branchId);
sqlCommand.Parameters.AddWithValue("#Flag", 18);
var data = PrjClass.GetData(sqlCommand);
txtMemberShip.Text = data.Tables[0].Rows[0]["MembershipId"].ToString();
txtBarCode.Text = data.Tables[0].Rows[0]["Barcode"].ToString();
}
It's working fine, but is is not updating any of the textboxes. Also, I checked in watch window, the values are returned as expected (M-1213 and 634-98-4 ) and the code does reaches the point txtMemberShip.Text = data.Tables[0].Rows[0]["MembershipId"].ToString();
but the txtMemberShip just remains empty??? Can anyone tell me why is not updating the textboxes?
UPDATE
As per comments, here is the page load
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindDropDown();
BindGrid();
SetDefaultsInTextBoxes();
}
}
And I don't have any code that waits on this task.

Answer 1

Don't do this:
Task.Factory.StartNew(() => FillMemberShipAndBarCode(dsMain.Tables[0].Rows[0]["CustomerCode"].ToString(), Ob.BranchId));
What are you trying to achieve by doing so?
What is probably happening is your method FillMemberShipAndBarCode is probably running after ASP.NET has already sent the page back to the browser. Thus, essentially, no visible effect on the rendered HTML.
ASP.NET isn't a good place to do multi-threaded stuff.
Try just replacing the above with this:
FillMemberShipAndBarCode(dsMain.Tables[0].Rows[0]["CustomerCode"].ToString(), Ob.BranchId);