#1 Params

A simple question. What would be printed out after execution?

void Main()
{
 Foo();
 Foo(null)
 Foo(null as object)
}

void Foo(params object[] args)
{
 if (args == null)
  Console.WriteLine("Null");
 else
  Console.WriteLine(args.Length);
}

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#3 Enum.ToString()

It's kinda surprise, but Enum.ToString() uses reflection to get a string representation of an enum:

public override string ToString()
{
  Type type = base.GetType();
  object obj2 = ((RtFieldInfo) GetValueField(type)).InternalGetValue(this, false);
  return InternalFormat(type, obj2);
}

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This approach leads to visible performance issues when an application widely uses enum.ToString() (Obviously, any enum).

This issue could be fixed with the following trick code:

static class EnumHelper
{
  static class Cache<T>
  {
    internal static readonly Dictionary<T, string> Values = new Dictionary<T, string>();
  }
    
  public static string FastToString<T>(this T @enum) where T:struct
  { 
    if (!typeof(T).IsEnum)
      throw new ArgumentException(string.Format("Type {0} is not an enumeration.", typeof(T)));
    lock (Cache<T>.Values)
    {
      string result;
      if (!Cache<T>.Values.TryGetValue(@enum, out result))
      {
        result = @enum.ToString();
        Cache<T>.Values.Add(@enum, result);
      }
      return result;
    }
  }
}

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And, of course, all enum.ToString() should be replaced with enum.FastToString().

Total Commander Find Files and Subversion

When you're trying to search some file in a folder under subversion control, you receive a slight performance degradation, especially when you trying to find some text inside files. Total Commander tries to search inside ".svn" files and folders.
There is a good trick for such cases - Total Commander supports some tiny syntax to be used in "Search for:" field. So to exclude some files or folders from the search, you can put them into "Search field:" after a '|' sign. Note that wildcards can be used in include/exclude directory names, and the names must have a trailing backslash '\'.

For example:

• w*.*|*.bak *.old finds files, which start with w and do not end with .bak or .old.
  
• SomeFile.cs | .svn\ finds 'SomeFile.cs' not looking into subversion folders.
  

#2.5 Usings and Enumerators

One more thing regrading using. Do not forget, that IEnumerator<T> is IDisposable (though, IEnumerator is not).

public interface IEnumerator<T> : IDisposable, IEnumerator
{
  // Properties
  T Current { get; }
}


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So do not forget to enclose GetEnumerator() calls to using statement.

#2 Usings

Just not to forget, that there could be multiple objects in a using statement:

using (Font font3 = new Font("Arial", 10.0f),
      font4 = new Font("Arial", 10.0f))
{
  // Use font3 and font4.
}

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Though, all objects should be of the same type, the following is not allowed:

using (IEnumerator<T1> firstEnumerator = first.GetEnumerator(),
    IEnumerator<T2> secondEnumerator = second.GetEnumerator())
{
  // ...
}

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