asp.net select multiple table

your question is not clear, but i think this may help you

declare SqlConnection con with desired connection string, SqlCommand cmd, SqlDataReader reader, string selectSQL and 2 ComboBox combobox1&combobox2

selectSQL = "SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES";
cmd = new SqlCommand(selectSQL, con);
con.Open();
reader = cmd.ExecuteReader();
while (reader.Read())
{
     comboBox1.Items.Add(reader.GetString(0).ToString());
}
reader.Close();

use below code in SelectedIndexChanged event of combobox

selectSQL = "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = "+"'"+comboBox1.Text+"'";
cmd = new SqlCommand(selectSQL, con);
reader = cmd.ExecuteReader();
while (reader.Read())
{
     comboBox2.Items.Add(reader.GetString(0).ToString());
}
reader.Close();

--theanil