PostProcessWSA.CheckImageConsistencyAndGetName C# (CSharp) Method

    protected string CheckImageConsistencyAndGetName(params string[] strings)
    {
        string str = null;
        string a = null;
        foreach (string str3 in strings)
        {
            if (!string.IsNullOrEmpty(str3))
            {
                if (str == null)
                {
                    str = str3;
                    a = Path.GetExtension(str3);
                }
                else if (!string.Equals(a, Path.GetExtension(str3), StringComparison.InvariantCultureIgnoreCase))
                {
                    throw new Exception(string.Format("Inconsistency between images in the same group ({0}). All images should be either PNG or JPEG!", str));
                }
            }
        }
        return str;
    }