Logging in SharePoint 2010 Custom Applications using SharePoint SPDiagnosticsServiceBase Class.

In SharePoint 2010 we have a very easy way to log errors in default SharePoint Log at "14\Log" folder by default. However if you are not able to view it here you can check Central Administrator --> Monitoring -->
Configure Diagonistic Logging -->Trace Log. Here is the code for :

Add  a class file into your project and then paste below code :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Administration;
using System.Runtime.InteropServices;


namespace LoggingServiceExample
{
    public class LoggingService : SPDiagnosticsServiceBase
    {
        public static string vsDiagnosticAreaName = "SharePoint Logging Service";
        public static string CategoryName = "SharePointProject";
        public static uint uintEventID = 700; // Event ID
        private static LoggingService _Current;
        public static LoggingService Current
        {
            get
            {
                if (_Current == null)
                {
                    _Current = new LoggingService();
                }
                return _Current;
            }
        }
        private LoggingService()
            : base("SharePoint Logging Service", SPFarm.Local)
        { }
        protected override IEnumerable<SPDiagnosticsArea> ProvideAreas()
        {
            List<SPDiagnosticsArea> areas = new List<SPDiagnosticsArea>
                 {
                  new SPDiagnosticsArea(vsDiagnosticAreaName, new List<SPDiagnosticsCategory>
                   {
                    new SPDiagnosticsCategory(CategoryName, TraceSeverity.Medium, EventSeverity.Error)
                   })
                  };
            return areas;
        }
        public static string LogErrorInULS(string errorMessage)
        {
            string strExecutionResult = "Message Not Logged in ULS. ";
            try
            {
                SPDiagnosticsCategory category = LoggingService.Current.Areas[vsDiagnosticAreaName].Categories[CategoryName];
                LoggingService.Current.WriteTrace(uintEventID, category, TraceSeverity.Unexpected, errorMessage);
                strExecutionResult = "Message Logged";
            }
            catch (Exception ex)
            {
                strExecutionResult += ex.Message;
            }
            return strExecutionResult;
        }
        public static string LogErrorInULS(string errorMessage, TraceSeverity tsSeverity)
        {
            string strExecutionResult = "Message Not Logged in ULS. ";
            try
            {
                SPDiagnosticsCategory category = LoggingService.Current.Areas[vsDiagnosticAreaName].Categories[CategoryName];
                LoggingService.Current.WriteTrace(uintEventID, category, tsSeverity, errorMessage);
                strExecutionResult = "Message Logged";
            }
            catch (Exception ex)
            {
                strExecutionResult += ex.Message;
            }
            return strExecutionResult;
        }
    }
}

You just need to call following code on each entry points for any custom component :

try
{
            
}
catch(Exception ex)
 {
LoggingService.LogErrorInULS("Custom SharePoint Application exception at " + System.DateTime.Now + "Exception Message : "+ ex.Message.ToString() +" Exception Stacktrace : "+ ex.StackTrace.ToString());
}

Hope it helps..!!