Enforcing Input Parameters to a Method without a bunch of if's at the beginning of the method?

public string SomeFunction(string param1, int param2)
{
    if(string.IsNullOrEmpty(param1)){
        throw new ArgumentException("bla", "param1");
    }
    if(param2 < 0 || param2 > 100 || param2 == 53)
    {
         throw new ArgumentOutOfRangeException("eek", "param2");
    }
}

public string SomeFunction(string param1, int param2)
{
    CheckParameterNotNull(param1);
    CheckParameterRange(param2, 0, 100, 53);
...
}

private string InternalSomeFunction(string param1, int param2)
{
  /* implementation goes here */
}

public string SomeFunction(string param1, int param2)
{
  if (string.IsNullOrEmpty(param1)) {
    throw new ArgumentException("bla", "param1");
  }
  if (param2 < 0 || param2 > 100 || param2 == 53) {
    throw new ArgumentOutOfRangeException("eek", "param2");
  }
  return InternalSomeFunction(param1, param2);
}

if (IsFormValid)
{
   // Processing Magic Goes here.
}