在while条件中使用未分配的局部变量和“无法写入已关闭的TextWriter”。

Anastasia 发表于 Dev

阿纳斯塔西娅

我尝试了这段代码，但是在while条件下继续使用未分配的局部变量MAX_VALUE。（现在已修复），但是现在出现“无法写入封闭的TextWriter”。用于WriteLine输出文件。请帮忙

    private void buttonCalculate_Click(object sender, EventArgs e)
    {
        double kmph;
        double MAX_VALUE;

        if (double.TryParse(textBoxSpeed.Text, out kmph) && (double.TryParse(textBoxHours.Text, out MAX_VALUE)))

        outputFile = File.CreateText("Output.txt");

        int count = 1;

        while (count <= MAX_VALUE)
        {
            outputFile.WriteLine("After hour " + count + "the distance traveled is " + kmph * count + "Km.");

            count = count + 1;

            outputFile.Close();

            MessageBox.Show("Outputs are saved to Output.txt file.");
        }
    }

    private void buttonExit_Click(object sender, EventArgs e)
    {
        this.Close();

阿德里安·埃福德（Adrian Efford）

如果{在if语句之后缺少您，那么使用未分配变量的代码将始终被执行并引发异常：

        //I'm not sure if you want to continue writing or every time you enter the function rewrite the file...
        //This is an example in case you want to continue writing
        var filePath = "C:\\myPath";
        if (!File.Exists(filePath))
        {
            //If file doesn't exist create one
            File.CreateText(filePath);
        }

        var outputFile = File.AppendText(filePath); //open file to write

        if (double.TryParse(textBoxSpeed.Text, out kmph) && (double.TryParse(textBoxHours.Text, out MAX_VALUE)))
        {

            outputFile = File.CreateText("Output.txt");

            int count = 1;

            while (count <= MAX_VALUE)
            {
                outputFile.WriteLine("After hour " + count + "the distance traveled is " + kmph * count + "Km.");

                count = count + 1;


                MessageBox.Show("Outputs are saved to Output.txt file.");
            }

            outputFile.Flush();
            outputFile.Close();
        }

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