Full repo available at https://bitbucket.org/createdbyx/codefarts.utilities-extension-methods-only

/// <summary>
/// Determines weather or not all the characters in a string are all the same.
/// </summary>
/// <param name="value">The value to check for.</param>
/// <returns>true is all characters are the same, otherwise false.</returns>
public static bool AllTheSame(this string value)
{
#if UNITY3D
    if (!StringExtensionMethods.IsNullOrWhiteSpace(value))
#else
    if (!string.IsNullOrWhiteSpace(value))
#endif
    {
        var clone = new string(value[0], value.Length);
        return clone == value;
    }

    return false;
}

#if UNITY3D
public static bool IsNullOrWhiteSpace(this string value)
{
    if (value == null)
    {
        return true;
    }

    for (var i = 0; i < value.Length; i++)
    {
        if (!char.IsWhiteSpace(value[i]))
        {
            return false;
        }
    }

    return true;
}
#endif
}