private void button2_Click(object sender, EventArgs e)        

{           

 this.dataGridView1.EndEdit();            

SqlConnection conn = new SqlConnection("server=.;integrated security=SSPI;database=test");            SqlCommand cmd = new SqlCommand("select * from a", conn); 

DataTable dt = new DataTable();           

 DataSet ds = new DataSet();            

SqlDataAdapter da = new SqlDataAdapter();            

cmd.CommandType = CommandType.Text;            

da.SelectCommand = cmd;            

da.Fill(ds, "a");            

SqlCommandBuilder cb = new SqlCommandBuilder();            

try           

 {               

 SqlCommandBuilder SCB = new SqlCommandBuilder(da);                

da.Update(dt);            

}            

catch (System.Exception ex)            

{                

MessageBox.Show(ex.ToString());                

return;           

 }        

}