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)
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
strmsg.Where(s => s.StartsWith("Info:")).ToArray());
Console.WriteLine("Info Log Created");
catch (Exception ex)
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:
strmsg.Where(s => s.StartsWith("Info:")).ToArray())