Log a String Collection in .NET

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I was working on a .NET 4 standalone application and wanted to write a simple routine to log messages to a text file for later analysis. Here’s how I created a List<string> and wrote it to a Log file using the File.WriteAllLines method. The WriteAllLines method creates a new file, writes a collection of strings to the file, and then closes the file. If the file already exists, it is overwritten, but you can get around this by creating random time-stamped file names.

In the code shown below, we add a few items to the List<String> depicting Info, Errors and Warning messages. We then use the WriteAllLines method and a simple expression to filter out ‘Info’ messages and write it to a log file.

static void Main(string[] args)
{
    try
    {
        List<string> strmsg = new List<string>();
        // Sample Log messages
        strmsg.Add("Info: Customer Record Added");
        strmsg.Add("Warning: Disallowed operations");
        strmsg.Add("Info: User Logged in");
        strmsg.Add("Error: Incorrect Customer");
        strmsg.Add("Info: Email Sent to the User");

        // write all Info messages to the log file
        File.WriteAllLines(@"C:\Logs\info.log",
            strmsg.Where(s => s.StartsWith("Info:")).ToArray());
        Console.WriteLine("Info Log Created");
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }

    Console.ReadLine();
}

Note: If you are using .NET Framework 3.5 or earlier, you will have to convert the IEnumerable<string> to an array, as .NET 3.5 does not have an overloaded method that accepts an IEnumerable<string>. In .NET 3.5, use the following piece of code:

File.WriteAllLines(@"C:\Logs\info.log",
    strmsg.Where(s => s.StartsWith("Info:")).ToArray())

OUTPUT

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About The Author

Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.