C# 修改StreamReader以在未找到文件时提供错误消息

救命啊！我对C#和代码非常陌生，只是偶尔会用到，所以请温柔一点

我正在尝试创建一种“更友好”的方法来打开文本文件进行阅读，如果在试图打开文件时无法找到该文件，那么这种方法将为用户提供更友好的信息。 为此，我创建了自己的“TextFileStreamReader”类。这与StreamReader基本相同，但如果找不到文件，则会显示一些错误消息。如果成功找到该文件，我希望返回一个实例StreamReader。但我不认为我可以这么做

关于我应该如何实现我想做的事情，有什么提示吗

//Trying to create a gentler class to a text file for reading
public class TextFileStreamReader : StreamReader
{
    public static TextFileStreamReader(string fullfilename) : base(string)
    {
        try
        {
            StreamReader reader = new StreamReader(fullfilename);
            Console.WriteLine("File {0} successfully opened.", fullfilename);
            return reader;  //Can't do this - but how do I return a StreamReader?
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
            "Can not find file {0}.", fullfilename);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
            "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
            "Can not open the file {0}", fullfilename);
        }
    }
}

预期用途

TextFileStreamReader myreader = New TextFileStreamReader("C:\Test\TestFile.txt");

---

您可以这样做：

public class TextFileStreamReader
{
    private string _FullFileName;

    public TextFileStreamReader(string fullfilename)
    {
        _FullFileName = fullfilename;
    }

    public StreamReader GetStream()
    {
        try
        {
            StreamReader reader = new StreamReader(_FullFileName);
            Console.WriteLine("File {0} successfully opened.", _FullFileName);
            return reader;  //Can't do this - but how do I return a StreamReader?
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
            "Can not find file {0}.", _FullFileName);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
            "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
            "Can not open the file {0}", _FullFileName);
        }
        return null;
    }

}

TextFileStreamReader tfsr = new TextFileStreamReader("fullfilename");
StreamReader sr = tfsr.GetStream();
//...

然后像这样称呼这个班：

public class TextFileStreamReader
{
    private string _FullFileName;

    public TextFileStreamReader(string fullfilename)
    {
        _FullFileName = fullfilename;
    }

    public StreamReader GetStream()
    {
        try
        {
            StreamReader reader = new StreamReader(_FullFileName);
            Console.WriteLine("File {0} successfully opened.", _FullFileName);
            return reader;  //Can't do this - but how do I return a StreamReader?
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
            "Can not find file {0}.", _FullFileName);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
            "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
            "Can not open the file {0}", _FullFileName);
        }
        return null;
    }

}

TextFileStreamReader tfsr = new TextFileStreamReader("fullfilename");
StreamReader sr = tfsr.GetStream();
//...

---

您可以这样做：

public class TextFileStreamReader
{
    private string _FullFileName;

    public TextFileStreamReader(string fullfilename)
    {
        _FullFileName = fullfilename;
    }

    public StreamReader GetStream()
    {
        try
        {
            StreamReader reader = new StreamReader(_FullFileName);
            Console.WriteLine("File {0} successfully opened.", _FullFileName);
            return reader;  //Can't do this - but how do I return a StreamReader?
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
            "Can not find file {0}.", _FullFileName);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
            "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
            "Can not open the file {0}", _FullFileName);
        }
        return null;
    }

}

TextFileStreamReader tfsr = new TextFileStreamReader("fullfilename");
StreamReader sr = tfsr.GetStream();
//...

然后像这样称呼这个班：

public class TextFileStreamReader
{
    private string _FullFileName;

    public TextFileStreamReader(string fullfilename)
    {
        _FullFileName = fullfilename;
    }

    public StreamReader GetStream()
    {
        try
        {
            StreamReader reader = new StreamReader(_FullFileName);
            Console.WriteLine("File {0} successfully opened.", _FullFileName);
            return reader;  //Can't do this - but how do I return a StreamReader?
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
            "Can not find file {0}.", _FullFileName);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
            "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
            "Can not open the file {0}", _FullFileName);
        }
        return null;
    }

}

TextFileStreamReader tfsr = new TextFileStreamReader("fullfilename");
StreamReader sr = tfsr.GetStream();
//...

---

您可以使用以下类为给定的文件路径创建流，该文件路径将允许您使用所需的用法，即使用一行调用代码创建流：

public class TextFileStreamReader
{
    /// <summary>
    /// Creates an instance of the StreamReaer class for a given file path.
    /// </summary>
    /// <param name="path">The complete file path to be read.</param>
    /// <returns>A new instance of the StreamReader class if the file was successfully read, otherwise null.</returns>
    public static StreamReader CreateStream(string path)
    {
        try
        {
            var reader = new StreamReader(path);

            Console.WriteLine(
                "File {0} successfully opened.",
                path);

            return reader;
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
                "Can not find file {0}.",
                path);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
                "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
                "Can not open the file {0}",
                path);
        }

        return null;
    }
}

---

在使用streamReader变量之前，您显然需要检查它是否为null，但这应该满足您的要求。

您可以使用以下类为给定的文件路径创建流，该文件路径将允许您使用所需的用法，即使用一行调用代码创建流：

public class TextFileStreamReader
{
    /// <summary>
    /// Creates an instance of the StreamReaer class for a given file path.
    /// </summary>
    /// <param name="path">The complete file path to be read.</param>
    /// <returns>A new instance of the StreamReader class if the file was successfully read, otherwise null.</returns>
    public static StreamReader CreateStream(string path)
    {
        try
        {
            var reader = new StreamReader(path);

            Console.WriteLine(
                "File {0} successfully opened.",
                path);

            return reader;
        }
        catch (FileNotFoundException)
        {
            Console.Error.WriteLine(
                "Can not find file {0}.",
                path);
        }
        catch (DirectoryNotFoundException)
        {
            Console.Error.WriteLine(
                "Invalid directory in the file path.");
        }
        catch (IOException)
        {
            Console.Error.WriteLine(
                "Can not open the file {0}",
                path);
        }

        return null;
    }
}

---

在使用streamReader变量之前，您显然需要检查它是否为null，但这应该满足您的要求。

非常感谢您的帮助，Wudge。这绝对是一个进步（因为它确实有效！），但我希望能够用一条线做任何事情。看来这一定是一种方法，但我不知道该怎么做。非常感谢你的帮助，Wudge。这绝对是一个进步（因为它确实有效！），但我希望能够用一条线做任何事情。看来这一定是一种方法，但我不知道怎么做。谢谢艾伦！这正是我想要的。我惊讶地看到，您不必实例化TextFileStreamReader类的实例，但可以使用StreamReader StreamReader=TextFileStreamReader.CreateStream（@“C:\Test\TestFile.txt”）直接引用它；别担心，刺猬。可以在不实例化TextFileStreamReader类实例的情况下调用CreateStream（）方法的原因是该方法被标记为静态，这意味着它不需要调用该类的实例。哈你的解释很有帮助，链接也是如此。突然，很多事情都发生了！谢谢你，艾伦！这正是我想要的。我惊讶地看到，您不必实例化TextFileStreamReader类的实例，但可以使用StreamReader StreamReader=TextFileStreamReader.CreateStream（@“C:\Test\TestFile.txt”）直接引用它；别担心，刺猬。可以在不实例化TextFileStreamReader类实例的情况下调用CreateStream（）方法的原因是该方法被标记为静态，这意味着它不需要调用该类的实例。哈你的解释很有帮助，链接也是如此。突然，很多事情都发生了！