private void FLoadDataGrid()  
{
try
  {
     string strSql = "Select   FirstName, LastName from TblCustomer ";  
     sqlConn = new SqlConnection(connStr);
     sqlConn.Open();
    DA = new SqlDataAdapter(strSql, sqlConn);
    DS =   new DataSet("DS");
 
    //Clear dataset before refill 
   DS.Clear();
   DS.CaseSensitive = true;
   DA.Fill(DS,"PatientTbl");
 
   //declare datatable
   DataTable DT = new DataTable();
   DT.Clear();
   DT = DS.Tables[0];
 
    DataColumn colNewDGCol = new DataColumn();
   colNewDGCol.DataType = System.Type.GetType("System.Boolean");
   colNewDGCol.DefaultValue = false;
   colNewDGCol.ColumnName = ("Selected");
   DT.Columns.Add(colNewDGCol);
 
   //... file datagrid
   FFormatDataGridColumn();
   dataGrid1.DataSource = DT; 
 }
catch (Exception Ex)
   {
       MessageBox.show(Ex.Message);
    }
finally
   {
      sqlConn.Close();
   }
 }

private void FFormatDataGridColumn()
 //define column structure for datagrid
{
   // declare tablestyle
  DataGridTableStyle DGStyle;  
  DGStyle = new DataGridTableStyle();  
  DGStyle.MappingName = "PatientTbl";   
 
  //checkbox column
  DataGridBoolColumn chkboxCol = new DataGridBoolColumn();
  chkboxCol.MappingName = "Selected";
  chkboxCol.HeaderText = "";
  chkboxCol.Width = 50;
  DGStyle.GridColumnStyles.Add(chkboxCol);
 
 //Firstname textbox column
    DataGridColumnStyle colFName = new DataGridTextBoxColumn();
   colFName.MappingName = "FirstName";
   colFName.HeaderText = "First Name";
   colFName.Width = 150;
   DGStyle.GridColumnStyles.Add(colFName);
 
  //lastName textbox column
    DataGridColumnStyle colLName = new DataGridTextBoxColumn();
   colLName.MappingName = "LastName";
   colLName.HeaderText = "Last Name";
   colLName.Width = 150;
  DGStyle.GridColumnStyles.Add(colLName);
 
// add table style to the dataGrid
   this.dataGrid1.TableStyles.Add(DGStyle);    
}