Break it down into smaller methods. Each if and each else should be their own class. Study up on refactoring and design patterns.

>But how do you navigate in all this if else code
>
>E.g.
>

>Int32 SomeValue;
>
>If (!Int32.TryParse(SomeString, out SomeValue) || SomeValue = 0)
>   {
>   // First Error here
>   }
>   else
>      { more code that may cause problems
>             if ...
>                     
>      }
>}

>
>In other words, it is very hard to keep track of all these if else and {}
>
>BTW, I usually create several UnitTests per method - for invalid parameters, for some unreal values, etc.