System.Security.SecurityException when writing to Event Log

To give Network Service read permission on the EventLog/Security key (as suggested by Firenzi and royrules22) follow instructions from http://geekswithblogs.net/timh/archive/2005/10/05/56029.aspx

1. Open the Registry Editor:
   1. Select Start then Run
   2. Enter regedt32 or regedit

2. Navigate/expand to the following key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\Security

3. Right click on this entry and select Permissions

4. Add the Network Service user

5. Give it Read permission

UPDATE: The steps above are ok on developer machines, where you do not use deployment process to install application.
However if you deploy your application to other machine(s), consider to register event log sources during installation as suggested in SailAvid's and Nicole Calinoiu's answers.

I am using PowerShell function (calling in Octopus Deploy.ps1)

function Create-EventSources() {
    $eventSources = @("MySource1","MySource2" )
    foreach ($source in $eventSources) {
            if ([System.Diagnostics.EventLog]::SourceExists($source) -eq $false) {
                [System.Diagnostics.EventLog]::CreateEventSource($source, "Application")
            }
    }
}

The problem is that the EventLog.SourceExists tries to access the EventLog\Security key, access which is only permitted for an administrator.

A common example for a C# Program logging into EventLog is:

string sSource;
string sLog;
string sEvent;

sSource = "dotNET Sample App";
sLog = "Application";
sEvent = "Sample Event";

if (!EventLog.SourceExists(sSource))
    EventLog.CreateEventSource(sSource, sLog);

EventLog.WriteEntry(sSource, sEvent);
EventLog.WriteEntry(sSource, sEvent, EventLogEntryType.Warning, 234);

However, the following lines fail if the program hasn't administrator permissions and the key is not found under EventLog\Application as EventLog.SourceExists will then try to access EventLog\Security.

if (!EventLog.SourceExists(sSource))
    EventLog.CreateEventSource(sSource, sLog);

Therefore the recommended way is to create an install script, which creates the corresponding key, namely:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Application\dotNET Sample App

One can then remove those two lines.

You can also create a .reg file to create the registry key. Simply save the following text into a file create.reg:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Application\dotNET Sample App]