Can write to csv file but not append

问题

string pathDesktop = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
        string filePath = pathDesktop + "\\mycsvfile.csv";
        string delimter = ",";
        string a = "Enoelpro---[037,033,0,018,030,012,004,021,009,038,035,053,044,050,074,F,018,010,070,000]<Vulpix>[-][037,034,0,022,020,029,002,008,024,036,046,049,041,057,077,F,018,005,070,000]<Vulpix>[-] cual es mejor??";
        List<string[]> test = conv(a,"testrainer");
        int length = test.Count;

        using (TextWriter writer = File.CreateText(filePath))
        {
            for (int index = 0; index < length; index++)
            {
                writer.WriteLine(string.Join(delimter, test[index]));
            }
        }

So, at the momement, this works fine, except it doesn't keep the old data in the csv file. How can I modify this so instead of deleting the data, it simply appends to the data?

回答1:

File.CreateText Method (String)

This method is equivalent to the StreamWriter(String, Boolean) constructor overload with the append parameter set to false. If the file specified by path does not exist, it is created. If the file does exist, its contents are overwritten. Additional threads are permitted to read the file while it is open.

StreamWriter Constructor (String, Boolean)

Here second parameter, true to append data to the file; false to overwrite the file.

If you check the documentation for each method it cleary say the answers for your questions and also there is a suggetion in case of you need to append the file. Use StreamWriter constructor with path and append parameter (true)

回答2:

Can you please try with StreamWriter class?

If the file exists, it can be either overwritten or appended to. If the file does not exist, this constructor creates a new file.

Instead using TextWriter writer = File.CreateText(filePath) try to use

TextWriter writer = new StreamWriter(filePath, true);

If you pass true in constructor it should append text to file.

来源：https://stackoverflow.com/questions/40688047/can-write-to-csv-file-but-not-append