C#文字列がNullまたはnullであると判断する方法

文字列がNullまたはnullであると判断する方法

IsNullOrEmpty

p == null || p == “”

p == null && p.Length == 0: 861ms

(p +”“).Length == 0: 1050ms

テスト結果

テスト1-IsNull OrEmpty:943 ms-p==null‖p=":1093 ms-p==null‖p.Length==0:831 ms-(p+").Length==0:1115 msテスト2-IsNull OrEmpty:850 ms-p==null‖p=":1005 ms-p==null‖p.Length==0:847 ms-(p+").Length==0:1077 ms

結論

p==null‖p.Length==0最速

NullOrEmptyとp==null‖p.Length==0の差は小さい.

3.

Code

 var sw = new System.Diagnostics.Stopwatch();
            var p = default(string);
            var q = "";
            var r = "str";

            sw.Reset();
            sw.Start();
            for (var i = 1; i < 100000000; i++)
            {
                var pR = string.IsNullOrEmpty(p);
                var qR = string.IsNullOrEmpty(q);
                var rR = string.IsNullOrEmpty(r);
            }

            sw.Stop();
            Console.WriteLine("IsNullOrEmpty: " + sw.ElapsedMilliseconds.ToString() + "ms");

            sw.Reset();
            sw.Start();
            for (var total = 1; total < 100000000; total++)
            {
                var pR = p == null || p == "";
                var qR = q == null || q == "";
                var rR = r == null || r == "";
            }

            sw.Stop();
            Console.WriteLine("p == null || p == \"\": " + sw.ElapsedMilliseconds.ToString() + "ms");

            sw.Reset();
            sw.Start();
            for (var total = 1; total < 100000000; total++)
            {
                var pR = p == null || p.Length == 0;
                var qR = q == null || q.Length == 0;
                var rR = r == null || r.Length == 0;
            }

            sw.Stop();
            Console.WriteLine("p == null || p.Length == 0: " + sw.ElapsedMilliseconds.ToString() + "ms");

            sw.Reset();
            sw.Start();
            for (var total = 1; total < 100000000; total++)
            {
                var pR = (p +"").Length == 0;
                var qR = (q +"").Length == 0;
                var rR = (r +"").Length == 0;
            }

            sw.Stop();
            Console.WriteLine("(p +\"\").Length == 0: " + sw.ElapsedMilliseconds.ToString() + "ms");