SqlConnection.RetryLogicProvider 屬性

定義

命名空間:

Microsoft.Data.SqlClient

組件:

Microsoft.Data.SqlClient.dll

套件:

Microsoft.Data.SqlClient v5.2.0

取得或設定值，其指定繫結至這個命令的 SqlRetryLogicBaseProvider 物件。

public:
 property Microsoft::Data::SqlClient::SqlRetryLogicBaseProvider ^ RetryLogicProvider { Microsoft::Data::SqlClient::SqlRetryLogicBaseProvider ^ get(); void set(Microsoft::Data::SqlClient::SqlRetryLogicBaseProvider ^ value); };

public Microsoft.Data.SqlClient.SqlRetryLogicBaseProvider RetryLogicProvider { get; set; }

member this.RetryLogicProvider : Microsoft.Data.SqlClient.SqlRetryLogicBaseProvider with get, set

Public Property RetryLogicProvider As SqlRetryLogicBaseProvider

屬性值

SqlRetryLogicBaseProvider

當設定為 null (預設) 時，將會套用預設不可重試的提供者。

備註

您必須設定此屬性的值，才能開啟連接才會生效。

若要套用重試邏輯，請先執行下列步驟，再開啟連線：

1. 使用 SqlRetryLogicOption 類型定義組態參數。
2. SqlRetryLogicBaseProvider使用 類別的下列其中一個靜態方法來 SqlConfigurableRetryFactory 建立 ：
   • CreateFixedRetryProvider
   • CreateIncrementalRetryProvider
   • CreateExponentialRetryProvider
   • CreateNoneRetryProvider
3. 將 SqlRetryLogicBaseProvider 物件指派給 RetryLogicProvider 屬性。

注意

偵測可重試的例外狀況是重試模式的重要部分。 套用重試邏輯之前，請務必調查例外狀況，並選擇最適合您案例的重試提供者。 首先，記錄您的例外狀況並尋找暫時性錯誤。

注意

連線 逾時 會針對每次開啟的連接執行重新開機。 這兩個動作之間沒有時間重迭。

注意

除非已在應用程式組態檔中設定，否則不會啟用預設重試邏輯提供者。 如需詳細資訊，請參閱 可設定的重試邏輯和組態檔。

範例

下列範例會嘗試開啟與無效資料庫的連線，以模擬資料庫服務暫時無法使用的條件。 嘗試建立連接時 SqlConnection ，您應該手動建立資料庫。

using Microsoft.Data.SqlClient;

/// Detecting retriable exceptions is a vital part of the retry pattern.
/// Before applying retry logic it is important to investigate exceptions and choose a retry provider that best fits your scenario.
/// First, log your exceptions and find transient faults.
/// The purpose of this sample is to illustrate how to use this feature and the condition might not be realistic.
class RetryLogicSample
{
    private const string DefaultDB = "Northwind";
    private const string CnnStringFormat = "Server=localhost; Initial Catalog={0}; Integrated Security=true; pooling=false;";
    private const string DropDatabaseFormat = "DROP DATABASE {0}";

    // For general use
    private static SqlConnection s_generalConnection = new SqlConnection(string.Format(CnnStringFormat, DefaultDB));

    static void Main(string[] args)
    {
        // 1. Define the retry logic parameters
        var options = new SqlRetryLogicOption()
        {
            NumberOfTries = 5,
            MaxTimeInterval = TimeSpan.FromSeconds(20),
            DeltaTime = TimeSpan.FromSeconds(1)
        };

        // 2. Create a retry provider
        var provider = SqlConfigurableRetryFactory.CreateExponentialRetryProvider(options);

        // define the retrying event to report the execution attempts
        provider.Retrying += (object s, SqlRetryingEventArgs e) =>
            {
                int attempts = e.RetryCount + 1;
                Console.ForegroundColor = ConsoleColor.Yellow;
                Console.WriteLine($"attempt {attempts} - current delay time:{e.Delay} \n");
                Console.ForegroundColor = ConsoleColor.DarkGray;
                if (e.Exceptions[e.Exceptions.Count - 1] is SqlException ex)
                {
                    Console.WriteLine($"{ex.Number}-{ex.Message}\n");
                }
                else
                {
                    Console.WriteLine($"{e.Exceptions[e.Exceptions.Count - 1].Message}\n");
                }

                // It is not a good practice to do time-consuming tasks inside the retrying event which blocks the running task.
                // Use parallel programming patterns to mitigate it.
                if (e.RetryCount == provider.RetryLogic.NumberOfTries - 1)
                {
                    Console.WriteLine("This is the last chance to execute the command before throwing the exception.");
                    Console.WriteLine("Press Enter when you're ready:");
                    Console.ReadLine();
                    Console.WriteLine("continue ...");
                }
            };

        // Open the general connection.
        s_generalConnection.Open();

        try
        {
            // Assume the database is being created and other services are going to connect to it.
            RetryConnection(provider);
        }
        catch
        {
            // exception is thrown if connecting to the database isn't successful.
            throw;
        }
    }

    private static void ExecuteCommand(SqlConnection cn, string command)
    {
        using var cmd = cn.CreateCommand();
        cmd.CommandText = command;
        cmd.ExecuteNonQuery();
    }

    private static void RetryConnection(SqlRetryLogicBaseProvider provider)
    {
        // Change this if you already have a database with the same name in your database.
        string dbName = "Invalid_DB_Open";

        // Create a connection to an invalid database.
        using var cnn = new SqlConnection(string.Format(CnnStringFormat, dbName));
        // 3. Assign the `provider` to the connection
        cnn.RetryLogicProvider = provider;
        Console.WriteLine($"Connecting to the [{dbName}] ...");
        // Manually execute the following command in SSMS to create the invalid database while the SqlConnection is attempting to connect to it.
        // >> CREATE DATABASE Invalid_DB_Open;
        Console.WriteLine($"Manually, run the 'CREATE DATABASE {dbName};' in the SQL Server before exceeding the {provider.RetryLogic.NumberOfTries} attempts.");
        // the connection tries to connect to the database 5 times
        Console.WriteLine("The first attempt, before getting into the retry logic.");
        cnn.Open();
        Console.WriteLine($"Connected to the [{dbName}] successfully.");

        cnn.Close();

        // Drop it after test
        ExecuteCommand(s_generalConnection, string.Format(DropDatabaseFormat, dbName));
        Console.WriteLine($"The [{dbName}] is removed.");
    }
}