lost focus from dynamically generated textbox inside updated gridview

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C#

ASP.NET

I have generated texboxes in header of the gridview for filtering the data...gridview is inside updatepanel...my main problem is when i enter something in textbox...gridview show the output data...but textbox lost its focus...so, i have to click another time on textbox...solve this issue please...textboxes generated by following rowcreated event

protected void gridview_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.Header)
        {

            TextBox txtsearch1;
            
            for (int i = 0; i < e.Row.Cells.Count; i++)
            {
                
                txtsearch1 = new TextBox();
                txtsearch1.ID = e.Row.Cells[i].Text;
                
                txtsearch1.Attributes["placeholder"] = e.Row.Cells[i].Text;
             
                e.Row.Cells[i].Controls.Add(txtsearch1);
            }
        }
    }