比如你要連接一個(gè)Sql Server服務(wù)器，你有一個(gè)connection string, 但是不知道是否是正確的，你可以這樣：

var connection = new SqlConnection(connectionString);

connection.Open();

connection.Close();

如果整個(gè)過程中沒有異常拋出，則說明connectionString是指向一個(gè)Sql Server的服務(wù)器。但是，如果connectionString里邊的Data Source（或者Server）的值是錯(cuò)的，就要等很久——大約30秒——才能從connection.Open()這一句拋出異常。有沒有辦法讓這個(gè) 過程快一點(diǎn)呢？

你可以試著在connectionString里添加上: "Connection Timeout=3"，這指示超時(shí)時(shí)間為3秒。但是實(shí)際上效果還是一樣的，異常仍然要在30秒之后才會拋出。

你也可以試著用另一個(gè)線程去連接服務(wù)器，主線程在若干秒后調(diào)用該線程的 Abort()方法，但是，實(shí)驗(yàn)效果是行不通，因?yàn)槟莻€(gè)線程在connection.Open()里根本出不來，無法被Abort掉。

最后，我的解決方法還是采用后臺線程，只不過如果到期尚未成功，那就當(dāng)做失敗，然后把它扔到一邊去，不再理它了:

            //采用后臺線程來連接數(shù)據(jù)庫，以便在服務(wù)器輸入錯(cuò)誤的情況下，不用等待很長的時(shí)間才能得到一個(gè)錯(cuò)誤提示
            string error = null;
            var success = false;

            // ReSharper disable AccessToModifiedClosure
            // ReSharper disable UseObjectOrCollectionInitializer
            var thread = new Thread(() =>
                                        {
                                            try
                                            {
                                                connection.Open();
                                                connection.Close();

                                                success = true;
                                            }
                                            catch (SqlException ex)
                                            {
                                                error = ex.Message;
                                            }
                                            finally
                                            {
                                                if (connection.State == ConnectionState.Open)
                                                    connection.Close();
                                            }
                                        });
            // ReSharper restore AccessToModifiedClosure
            // ReSharper restore UseObjectOrCollectionInitializer
            thread.IsBackground = true;
            var sw = Stopwatch.StartNew();
            thread.Start();

            var timeout = TimeSpan.FromSeconds(3);
            while (sw.Elapsed < timeout)
                thread.Join(TimeSpan.FromMilliseconds(200));
            sw.Stop();

            if (!success)
            {
                throw new Exception(error ?? "連接數(shù)據(jù)庫超時(shí)，請檢查輸入的服務(wù)器是否正確。");
            }