Question

When exploring options for creating text files I stumbled across this behavior I cant explain

Both buttons will create a file

but when I create a file with button1 button2 generates an error.

This only occurs when the file is actually created.

After a file is created buttons 1 and two operate as expected

Sample code for a simple GUI program 2 buttons and a multilne text box enclosed

    string logFile;

    public Form1()
    {
        InitializeComponent();

        logFile = "test.txt";

    }

    private void button1_Click(object sender, EventArgs e)
    {

        if (!System.IO.File.Exists(logFile))
        {
            System.IO.File.Create(logFile);
            textBox1.AppendText("File Created\r\n");
        }
        else
        {
            textBox1.AppendText("File Already Exists\r\n");
        }

        System.IO.File.AppendText("aaa");

    }

    private void button2_Click(object sender, EventArgs e)
    {

        // 7 overloads for creation of the Stream Writer

        bool appendtofile = true;

        System.IO.StreamWriter sw;

        try
        {
            sw = new System.IO.StreamWriter(logFile, appendtofile, System.Text.Encoding.ASCII);
            sw.WriteLine("test");
            textBox1.AppendText("Added To File Created if Needed\r\n");
            sw.Close();

        }
        catch (Exception ex)
        {
            textBox1.AppendText("Failed to Create or Add\r\n");

            // note this happens if button 1 is pushed creating the file 
            // before button 2 is pushed 
            // eventually this appears to resolve itself

            textBox1.AppendText("\r\n");
            textBox1.AppendText(ex.ToString());
            textBox1.AppendText("\r\n");
            textBox1.AppendText(ex.Message);
        }



    }

Answer 1

You might be getting an error because file resource is in use by the previous process. While using resources like file (and using a StreamWriter object, which is IDisposable), it is advised to use the “Using” directive. This will close the resource once code execution completes.

 using (StreamWriter sw = File.CreateText(path)) 
            {
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }   

Once you write the third line, file will automatically be closed and resources disposed.