8

这是我的通用功能：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;

/// <summary>
/// Summary description for GeneralFunctions
/// </summary>
public class GeneralFunctions
{
    public GeneralFunctions ()
    {
        //
        // TODO: Add constructor logic here
        //
    }

    public static DataTable GetData ( string query )
    {
        SqlDataAdapter dataAdapter;
        DataTable table;

        try
        {
            dataAdapter = new SqlDataAdapter( query, GetConnectionString() );
            table = new DataTable();

            dataAdapter.Fill( table );
            return table;
        }
        catch ( Exception ex )
        {
        }
        finally
        {
            dataAdapter = null;
            table = null;
        }

        return table;
    }

    private static string GetConnectionString ()
    {
        string connectionString = ConfigurationManager.ConnectionStrings[ "CAPortalConnectionString" ].ConnectionString;

        return connectionString;
    }

    public static int? AuthenticateLogin ( string username, string password )
    {
        using ( var conn = new SqlConnection( GetConnectionString() ) )
        using ( var cmd = conn.CreateCommand() )
        {
            conn.Open();
            cmd.CommandText =
            @"SELECT 
                 DistID 
             FROM 
                 Distributor
             WHERE 
                 Username = @username 
             AND 
                 Password = @password";
            cmd.Parameters.AddWithValue( "@username", username );
            cmd.Parameters.AddWithValue( "@password", password );
            using ( var reader = cmd.ExecuteReader() )
            {
                if ( !reader.Read() )
                {
                    // no results found
                    return null;
                }
                return reader.GetInt32( reader.GetOrdinal( "DistID" ) );
            }
        }
    }

    public static string GetDistInfo ( int distID )
    {
        using ( var conn = new SqlConnection( GetConnectionString() ) )
        using ( var cmd = conn.CreateCommand() )
        {
            conn.Open();
            cmd.CommandText =
            @"SELECT 
                 FName + ' ' + LName AS Name
             FROM 
                 Distributor
             WHERE 
                 DistID = @distid";
            cmd.Parameters.AddWithValue( "@distid", distID );
            using ( var reader = cmd.ExecuteReader() )
            {
                return reader.GetString( reader.GetOrdinal( "Name" ) );
            }
        }
    }

}

这是我的登录页面：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class index : System.Web.UI.Page
{
    protected void Page_Load ( object sender, EventArgs e )
    {

    }
    protected void but_login_Click ( object sender, EventArgs e )
    {
        if ( username_id.Text != "" || password.Text != "" )
        {
            // Verify the username and password match the database
            var distId = GeneralFunctions.AuthenticateLogin( username_id.Text, password.Text );

            if ( distId != null )
            {
                // User is authenticated
                var name = GeneralFunctions.GetDistInfo( (int)distId );
                Session[ "DistName" ] = name;
                Session[ "DistID" ] = distId;

                Response.Redirect( "dashboard.aspx", false );
            }
            else
            {
                // provide error label here username and password do not match
                authentFailed.Text = "Username / Password did not match our records";
            }
        }
        else
        {
            // Username or Password blank error lable
            authentFailed.Text = "Please Input Username / Password";
        }
    }
}

在我添加 GetDistInfo 方法之前，它工作得很好，登录了用户。然后我尝试添加 Session 变量和 GetDistInfo 方法。我将从 AuthenticateLogin 返回的 DistID 传递给 GetDistInfo 方法。它出现以下错误：

异常详细信息：System.InvalidOperationException：不存在数据时尝试读取无效。

Source Error:

Line 95:             using ( var reader = cmd.ExecuteReader() )
Line 96:             {
Line 97:                 return reader.GetString( reader.GetOrdinal( "Name" ) );
Line 98:             }
Line 99:         }


Source File: c:\inetpub\wwwroot\Base\ClientAccessPortal\App_Code\GeneralFunctions.cs    Line: 97

当我对数据库运行 SQL 时，它正确地拉回了客户端名称。我不确定为什么它不在代码中这样做。任何人都能够看到我错过了什么？

4

2 回答 2

22

请尝试更换这个。实际上Read()在您的代码中丢失了。

using ( var reader = cmd.ExecuteReader() )
{
     return reader.GetString( reader.GetOrdinal( "Name" ) );
}

有以下

using ( var reader = cmd.ExecuteReader() )
{
     if(reader.Read())
     {
          return reader.GetString( reader.GetOrdinal( "Name" ) );
     }
     return null;
}
于 2012-04-13T18:32:10.667 回答
4

您需要先阅读（在代码中使用上面的阅读器时您正在这样做）：

using ( var reader = cmd.ExecuteReader() )
{
    // you haven't positioned yourself on a record yet.
    while (reader.Read())
    {
        return reader.GetString( reader.GetOrdinal( "Name" ) );
    }
    return string.Empty;
}

编辑 回应你得到的错误；因为你定义了你的功能

public static string GetDistInfo ( int distID )

“超出功能”的所有可能方式都必须返回一些东西。在您的情况下，您应该返回一个字符串或可能为 null，具体取决于您想要做什么。

于 2012-04-13T18:37:28.980 回答