IsEmptyOrWhiteSpace

//This method will check if a string is empty or consists only of whitespace characters, but not null or containing any other characters. This check is sometimes required in data validation processes.

public static bool IsEmptyOrWhiteSpace(this string value)
{
    return value != null && value.Trim() == string.Empty;
}

Assert.IsFalse(IsEmptyOrWhiteSpace(null));
Assert.IsTrue(IsEmptyOrWhiteSpace(string.Empty));
Assert.IsTrue(IsEmptyOrWhiteSpace("   "));
Assert.IsFalse(IsEmptyOrWhiteSpace("TestValue"));
Assert.IsTrue(IsEmptyOrWhiteSpace(""));