Convert problem with "date textmode" for textbox

protected void Grid_RowCommand(object sender, GridViewCommandEventArgs e) { if (e.CommandName == "ibutonsec") { int num = int.Parse(e.CommandArgument.ToString()); txtboxStartDate.Text = gridViewIsemri.Rows[num].Cells[2].Text; txtboxEndDate.Text = gridViewIsemri.Rows[num].Cells[4].Text; } }  Hi everyone 
I want to get StartTime and EndTime when i clicked blue button(You'll see above pic in gridview) . I can get time , text , numbers etc ... but i can't send value to date textbox from S ...