By default a SqlDataAdapter does not have any code to generate an insert command. Also, calling NewRow() doesn't add the row to the table.
Check out the documentation here:
http://msdn2.microsoft.com/en-us/lib...rtcommand.aspx
Also, if you make your variable names cslightly longer it will be easier to read your code:
SqlDataAdapter adapter = new SqlDataAdapter("Select * From Supplier_Master", con);
DataSet dataset = new DataSet();
adapter.Fill(dataset);
DataTable table = dataset.Tables[0];
DataRow row = table.NewRow();
row.ItemArray[0] =textbox1.Text;
row.ItemArray[1] = textbox2.text;
table.Rows.Add(row);
adapter.Update(dataset);
/- Sam Judson : Wrox Technical Editor -/