1.建立webservices
    [WebMethod]
    public DataSet ExecuteSQL(string sql)
    {
        DataSet ds = new DataSet();
        if (sqlconn == null)
            InitConn();
        if (sqlconn != null)
        {
            try
            {
                SqlDataAdapter sda = new SqlDataAdapter(sql, sqlconn);
                sda.Fill(ds);
            }
            catch (SqlException e)
            {
                Console.WriteLine("SqlException"+e.ToString());
            }
            catch (Exception e)
            {
                Console.WriteLine("Exception" + e.ToString());
            }
        }
        return ds;
    }
InitConn()函数:
    SqlConnection sqlconn = null;
    private void InitConn()
    {
        try
        {
            if (sqlconn == null)
                sqlconn = new SqlConnection("Data Source=<servername>;Initial Catalog=<dbname>;User ID=sa;Password=<pwd>;User Instance=False");
        }
        catch (Exception e)
        {
            System.Console.WriteLine(e.ToString());
            System.Console.WriteLine(e.StackTrace);
        }
    }
调用的方式如下:
private void button2_Click(object sender, EventArgs e)
        {
            Service s = new Service();
            s.Url = "http://localhost/MyWebServices/Service.asmx";
            try
            {
                DataSet ds = s.ExecuteSQL(this.textBox1.Text);
                this.dataGridView1.DataSource = ds.Tables[0].DefaultView;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }