How do I improve query performance to fill a combobox with 7800 rows

Select StockId,StockName from StockMaster;

DataTable dt_fill_StocksCombo = new DataTable();
                dt_fill_StocksCombo = con.select_AllStocks();
                ((GridViewDataComboBoxColumn)gdStocks.Columns["StockName"]).PropertiesComboBox.IncrementalFilteringMode = DevExpress.Web.ASPxEditors.IncrementalFilteringMode.StartsWith;
                ((GridViewDataComboBoxColumn)gdStocks.Columns["StockName"]).PropertiesComboBox.DropDownStyle = DevExpress.Web.ASPxEditors.DropDownStyle.DropDown;
                ((GridViewDataComboBoxColumn)gdStocks.Columns["StockName"]).PropertiesComboBox.DataSource = dt_fill_StocksCombo;
                ((GridViewDataComboBoxColumn)gdStocks.Columns["StockName"]).PropertiesComboBox.ValueField = "StockId";
                ((GridViewDataComboBoxColumn)gdStocks.Columns["StockName"]).PropertiesComboBox.TextField = "StockName";

public DataTable select_AllStocks()
       {
           Open_Connection();
           DataTable dt = new DataTable();
           cmd = new SqlCommand("sp_select_AllStocks", con);
           cmd.CommandType = CommandType.StoredProcedure;
           SqlDataAdapter adt = new SqlDataAdapter(cmd);
           adt.Fill(dt);
           Close_Connection();
           return dt;
       }