AssertArgument(
            bool condition,
            [NotNull, InvokerParameterName] string argName,
            [NotNull] string messageFormat,
            [CanBeNull] object arg)

NotNullNorWhiteSpace
NotNullNorContainsNull
ValidateRange // или Range|AssertRange? для ArgumentOutOfRangeException
ValidateIndexRange // или IndexRange|AssertIndexRange для для IndexOutOfRangeException

public static IEnumerable<T[]> Split<T>([NotNull] this IEnumerable<T> source, int size)
{
    Code.NotNull(source, nameof(source));

    // Вот здесь хотелось бы не if & throw, а что-то типа такого как пример:
    // Code.RangeValid(size > 0, nameof(size))
    // с выбросом нужного исключения.
    if (size <= 0)
        throw new ArgumentOutOfRangeException(nameof(size));

    return SplitImpl(source, size);
}

R>NotNullNorWhiteSpace
R>NotNullNorContainsNull
R>ValidateRange // или Range|AssertRange? для ArgumentOutOfRangeException
R>ValidateIndexRange // или IndexRange|AssertIndexRange для для IndexOutOfRangeException
R>

EnumerableCode.NotEmptyAndNoNulls(values, "...")
и
DebugEnumerableCode.AssertAll(values, v => v > 0); // только InvalidOperation, т.к. тут проблема с состоянием кода, а не с неверно переданными аргументами

IOCode.FileExists("myFile.txt", "...")
и
DebugIOCode.StreamHasContent(values, v => v > 0);

Code.ArgumentInRange(insertIndex, nameof(insertIndex), 0, Count);

Code.StateInRange(position, nameof(position), -1, Length);

Code.ValidIndex(index, nameof(index));
Code.ValidIndex(index, nameof(index), Count);

Code.AssertArgument(arg > 0 && arg < 10, nameof(arg), "Some message1");

Code.AssertState(IsInitialized, "Some message2"); // InvalidOperationException

Code.AssertBusiness(CheckSomePolicy(), "Some message3");  // BusinessException

Code.AssertWeb(timeout.TotalSeconds < 15, "Some message4"); // WebException

Code.NotDisposed(!disposed, GetType());

// или
Code.NotDisposed(file != null, GetType());

protected void AssertNotDisposed() => Code.DisposedIf(disposed, this);

In computer science, an invariant is a condition that can be relied upon to be true during execution of a program, or during some portion of it. It is a logical assertion that is held to always be true during a certain phase of execution. For example, a loop invariant is a condition that is true at the beginning and end of every execution of a loop.

Log(string message);
Log(string message, object arg);
Log(string message, object arg1, object arg2);
Log(string message, object arg1, object arg2, object arg3);
Log(string message, params object [] args);

Log<TArg>(string message, TArg arg);
Log<TArg1, TArg2>(string message, TArg1 arg1, TArg2 arg2);
...
Log(string message, params object [] args);

TValue GetValueOrDefault<TKey, TValue>([NotNull] this IDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue)

TResult GetValueOrDefault<TKey, TValue, TResult>([NotNull] this IDictionary<TKey, TValue> dictionary, TKey key, TResult defaultValue)
    where TValue: TResult