WebMethod failure
本文关键字:failure WebMethod | 更新日期: 2023-09-27 18:16:39
我在一个不连接到我的数据库的asmx页面上有以下webmethod。谁能告诉我我哪里出错了?
[WebMethod]
public int[] getEmployeeIDs()
{
Connection conn = new Connection();
Recordset rs = new Recordset();
conn.ConnectionString = "Data Source=MyWebBasedServer;Initial Catalog=MyDatabase;Persist Security Info=False;User ID=MyLogin;Password=MyPassword";
rs.Open("SELECT ID from MyTable", conn, CursorTypeEnum.adOpenStatic);
int[] ID = new int[rs.RecordCount];
int i = 0;
while (!rs.EOF)
{
ID[i++] = rs.Fields["ID"].Value;
rs.MoveNext();
}
rs.Close();
conn.Close();
return ID;
}
我得到的错误信息是
连接不能用于执行此操作。要么是在此上下文中已关闭或无效。(指向"int[] ID = new"int [rs.RecordCount];")
谢谢。
下面的代码显示了从ADO.Net中的SELECT语句检索结果集的两种常用方法。
有一个叫做ConnectionStrings.com的网站,它展示了连接到SQL Server以及许多其他类型的数据库的所有方法。
如果你是c#编程新手,在处理实现IDisposable的对象时,using语句是避免资源泄漏的好方法。
从WebMethod
返回复杂类型可能会导致错误。该方法的底层XML序列化器可能不知道如何处理某些类型。在这种情况下,XmlIncludeAttribute可用于提供显式类型信息。这里有一个MSDN线程讨论如何做到这一点。
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web.Services;
namespace ConsoleApplication19
{
public class Program
{
public static void Main(String[] args)
{
var connectionString = "Data Source=MyWebBasedServer;Initial Catalog=MyDatabase;Persist Security Info=False;User ID=MyLogin;Password=MyPassword;";
var a = GetEmployeeIDs_Version1(connectionString);
var b = GetEmployeeIDs_Version2(connectionString);
}
/* Version 1
Use a "while" loop to fill a WebData list and return it as an array. */
[WebMethod]
private static WebData[] GetEmployeeIDs_Version1(String connectionString)
{
using (var connection = new SqlConnection(connectionString))
{
connection.Open();
var commandText = "SELECT ID, SurName from MyTable";
using (var command = new SqlCommand() { Connection = connection, CommandType = CommandType.Text, CommandText = commandText })
{
using (var reader = command.ExecuteReader(CommandBehavior.CloseConnection))
{
var result = new List<WebData>();
while (reader.Read())
result.Add(new WebData() { ID = Convert.ToInt32(reader["ID"]), Surname = reader["Surname"].ToString() });
return result.ToArray();
}
}
}
}
/* Version 2
Fill a DataSet with the result set.
Because there's only one SELECT statement, ADO.Net will
populate a DataTable with that result set and put the
DataTable in the dataset's Tables collection.
Use LINQ to convert that table into a WebData array. */
[WebMethod]
private static WebData[] GetEmployeeIDs_Version2(String connectionString)
{
using (var connection = new SqlConnection(connectionString))
{
connection.Open();
var commandText = "SELECT ID, SurName from MyTable";
using (var command = new SqlCommand() { Connection = connection, CommandType = CommandType.Text, CommandText = commandText })
{
using (var adapter = new SqlDataAdapter())
{
var dataSet = new DataSet();
adapter.SelectCommand = command;
adapter.Fill(dataSet);
return
dataSet
// There should only be one table in the dataSet's Table's collection.
.Tables[0]
.Rows
// DataTable isn't LINQ-aware. An explicit cast is needed
// to allow the use of LINQ methods on the DataTable.Rows collection.
.Cast<DataRow>()
// The rows in a DataTable filled by an SqlDataAdapter
// aren't strongly typed. All of a row's columns are
// just plain old System.Object. Explicit casts are necessary.
.Select(row => new WebData() { ID = Convert.ToInt32(row["ID"]), Surname = row["Surname"].ToString() })
// Use LINQ to convert the IEnumerable<WebData> returned by
// the .Select() method to an WebData[].
.ToArray();
}
}
}
}
}
public class WebData
{
public Int32 ID { get; set; }
public String Surname { get; set; }
}
}