Make sure that your gridview property "AutoGeneratedColumns=true", becouse you dynamically bind records to the gridview...
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox1.SelectedValue != null)
{
PopulateGridView(comboBox1.SelectedValue.ToString());
}
}
and make sure that in above code "comboBox1.SelectedValue" is your table name..