ADO.NET 连接字符串错误

发布于 2024-11-08 13:19:45 字数 1031 浏览 0 评论 0原文

首先，我是 C# 编程新手。我创建了一个专用类，用于从 Visual Studio 2010 中 Web 服务应用程序的 app.config 获取连接字符串，如下代码所示。

在构建代码时，我通过 catch 块收到以下错误：

“名称‘连接’在当前上下文中不存在”。

显然连接超出了范围。

我该如何避免这个错误？
这里使用的 Dispose 方法是否正确？

public class FCSConnection : IDisposable
{
    public string GetDefaultConnectionString()
    {   
        string DefaultConnectionString = null;
        try
        {
            DefaultConnectionString = ConfigurationManager.AppSettings["ConnectionString"];
            SqlConnection connection = new SqlConnection(DefaultConnectionString);
            connection.Open();
            return DefaultConnectionString;
        }
        catch (Exception)
        {
            if (DefaultConnectionString != null)
            {
                connection.Dispose();
            }
        }
        return DefaultConnectionString;
    }

    public void Dispose()
    {
        throw new NotImplementedException();
    }        
}

原文

Firstly, am new to C# programming.
I have created a dedicated class to get the connection string from the app.config of a Web Services application in Visual Studio 2010 as per the code below.

On building the code I get the following error via the catch block:

"The name 'connection' does not exist in the current context".

Obviously connection is going out of scope.

How do I avoid this error?
Is the Dispose method being used correctly here?

public class FCSConnection : IDisposable
{
    public string GetDefaultConnectionString()
    {   
        string DefaultConnectionString = null;
        try
        {
            DefaultConnectionString = ConfigurationManager.AppSettings["ConnectionString"];
            SqlConnection connection = new SqlConnection(DefaultConnectionString);
            connection.Open();
            return DefaultConnectionString;
        }
        catch (Exception)
        {
            if (DefaultConnectionString != null)
            {
                connection.Dispose();
            }
        }
        return DefaultConnectionString;
    }

    public void Dispose()
    {
        throw new NotImplementedException();
    }        
}

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人心善变 2024-11-15 13:19:45

确切的编译器消息引用您的 catch 语句：

connection.Dispose();

这里，connection 是一个未知名称，因为它是在 try 块内声明的。

至于你的整个代码，我认为它也是错误的。如果您希望您的 FCSConnection 类封装 SQL 连接，您应该将 connection 声明为私有成员，然后将其处置在您的 Dispose() 中方法。

The exact compiler message refers to your catch statement:

connection.Dispose();

Here, connection is an unknown name, because it's declared inside the try block.

As for your entire code, I think it's also wrong. If you want your FCSConnection class to encapsulate the SQL connection, you should declare connection as a private member and then dispose it in your Dispose() method.

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夜无邪 2024-11-15 13:19:45

public class FCSConnection : IDisposable
{
    private SqlConnection connection = null;

    public string GetDefaultConnectionString()
    {   
        string defaultConnectionString = null;
        try
        {
            defaultConnectionString = ConfigurationManager.AppSettings["ConnectionString"];
            connection = new SqlConnection(defaultConnectionString);
            connection.Open(); // are you sure want to keep the connection being opened??
        }
        catch
        {
            Dispose();
        }
        return defaultConnectionString;
    }

    public void Dispose()
    {
        if (connection != null)
        {
            connection.Dispose();
            connection = null; // to avoid repeat dispose
        }
    }        
}

public class FCSConnection : IDisposable
{
    private SqlConnection connection = null;

    public string GetDefaultConnectionString()
    {   
        string defaultConnectionString = null;
        try
        {
            defaultConnectionString = ConfigurationManager.AppSettings["ConnectionString"];
            connection = new SqlConnection(defaultConnectionString);
            connection.Open(); // are you sure want to keep the connection being opened??
        }
        catch
        {
            Dispose();
        }
        return defaultConnectionString;
    }

    public void Dispose()
    {
        if (connection != null)
        {
            connection.Dispose();
            connection = null; // to avoid repeat dispose
        }
    }        
}

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