How to Capture error log using C#.Net?

Introduction

How to capture the errors from application and write it in a log file. We have to mention the directory path in Webconfig file.

Background

This code is to capture the error log in log file with all information.

The code

Code:

public class LogError
{
	private DateTime errorDt;
	private string src;
	private Exception errorInfo;
	public static string strDirectoryPath;
	public DateTime ErrorDate
	{
		get {return errorDt; }
		set { errorDt = value;}
	}
	public string ErrorSrc
	{
		get { return src; }
		set { src = value; }
	}
	public Exception ErrorInformation
	{
		get { return errorInfo; }
		set { errorInfo = value; }
	}
 
	public static void Log_Err(string strErrorSource, Exception Ex)
	{
		LogError errInfo = new LogError();
		errInfo.ErrorDate = System.DateTime.Now;
		errInfo.ErrorSrc = strErrorSource;
		errInfo.ErrorInformation = Ex;
		LogError.LogErr(errInfo); 
	}
 
 
	public static void LogErr(LogError errorDTO)
	{
		try
		{
			string directoryPath = strDirectoryPath;
			if (!string.IsNullOrEmpty(strDirectoryPath))
			{
				string path = directoryPath + "\\" + "ErrorLog.txt";
				StreamWriter swErrorLog = null;
				DirectoryInfo dtDirectory = null;
				if (!Directory.Exists(directoryPath))
				{
					dtDirectory = Directory.CreateDirectory(directoryPath);
					dtDirectory = null;
				}
				if (File.Exists(path))
				{
					swErrorLog = new StreamWriter(path, true); //append the error message
					swErrorLog.WriteLine("Date and Time of Exception: " + errorDTO.ErrorDate);
					swErrorLog.WriteLine("Source of Exception: " + errorDTO.ErrorSrc);
					swErrorLog.WriteLine(" ");
					swErrorLog.WriteLine("Error Message: " + errorDTO.ErrorInformation);
					swErrorLog.WriteLine("------------------------------------------- ");
					swErrorLog.WriteLine(" ");
					//swErrorLog.WriteLine(System.Security.Principal.WindowsIdentity.GetCurrent().Name);
					swErrorLog.Close();
					swErrorLog = null;
				}
				else
				{
					swErrorLog = File.CreateText(path);
					swErrorLog = new StreamWriter(path, true); //append the error message
					swErrorLog.WriteLine("Date and Time of Exception: " + errorDTO.ErrorDate);
					swErrorLog.WriteLine("Source of Exception: " + errorDTO.ErrorSrc);
					swErrorLog.WriteLine(" ");
					swErrorLog.WriteLine("Error Message: " + errorDTO.ErrorInformation);
					swErrorLog.WriteLine("------------------------------------------- ");
					swErrorLog.WriteLine(" ");
					swErrorLog.Close();
					swErrorLog = null;
				}
			}
		}
		catch (NullReferenceException)
		{
			throw;
		} 
	}
}