// 连接字符串示例(包含连接池配置)
string connStr = "Data Source=server;Initial Catalog=db;User ID=user;Password=pass;Max Pool Size=100;Min Pool Size=10;";

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class MultiDbService : WebService
{
    // 多个数据库连接字符串
    private static readonly string PrimaryDbConnStr = ConfigurationManager.ConnectionStrings["PrimaryDB"].ConnectionString;
    private static readonly string SecondaryDbConnStr = ConfigurationManager.ConnectionStrings["SecondaryDB"].ConnectionString;
    
    [WebMethod]
    public DataSet GetDataFromMultipleSources()
    {
        DataSet result = new DataSet();
        
        // 第一个数据库连接
        using (SqlConnection conn1 = new SqlConnection(PrimaryDbConnStr))
        {
            SqlCommand cmd1 = new SqlCommand("SELECT * FROM Table1", conn1);
            SqlDataAdapter da1 = new SqlDataAdapter(cmd1);
            DataTable dt1 = new DataTable("Table1");
            da1.Fill(dt1);
            result.Tables.Add(dt1);
        }
        
        // 第二个数据库连接
        using (SqlConnection conn2 = new SqlConnection(SecondaryDbConnStr))
        {
            SqlCommand cmd2 = new SqlCommand("SELECT * FROM Table2", conn2);
            SqlDataAdapter da2 = new SqlDataAdapter(cmd2);
            DataTable dt2 = new DataTable("Table2");
            da2.Fill(dt2);
            result.Tables.Add(dt2);
        }
        
        return result;
    }
}

[WebMethod]
public bool UpdateMultipleDatabases()
{
    bool success = false;
    
    using (SqlConnection conn1 = new SqlConnection(PrimaryDbConnStr))
    using (SqlConnection conn2 = new SqlConnection(SecondaryDbConnStr))
    {
        conn1.Open();
        conn2.Open();
        
        using (SqlTransaction trans1 = conn1.BeginTransaction())
        using (SqlTransaction trans2 = conn2.BeginTransaction())
        {
            try
            {
                // 在第一个数据库执行操作
                SqlCommand cmd1 = new SqlCommand("UPDATE Table1 SET Col1=@value", conn1, trans1);
                cmd1.Parameters.AddWithValue("@value", "new value");
                cmd1.ExecuteNonQuery();
                
                // 在第二个数据库执行操作
                SqlCommand cmd2 = new SqlCommand("UPDATE Table2 SET Col2=@value", conn2, trans2);
                cmd2.Parameters.AddWithValue("@value", "new value");
                cmd2.ExecuteNonQuery();
                
                // 提交两个事务
                trans1.Commit();
                trans2.Commit();
                success = true;
            }
            catch
            {
                trans1.Rollback();
                trans2.Rollback();
                throw;
            }
        }
    }
    
    return success;
}