SqlCommand.RetryLogicProvider Proprietà

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

[System.ComponentModel.Browsable(false)]
public Microsoft.Data.SqlClient.SqlRetryLogicBaseProvider RetryLogicProvider { get; set; }

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

[<System.ComponentModel.Browsable(false)>]
member this.RetryLogicProvider : Microsoft.Data.SqlClient.SqlRetryLogicBaseProvider with get, set

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

Public Property RetryLogicProvider As SqlRetryLogicBaseProvider

Valore della proprietà

Se impostato su Null (impostazione predefinita), verrà usato il provider non retriable predefinito.

Attributi

BrowsableAttribute

Commenti

Prima dell'esecuzione del comando, è necessario impostare il valore per questa proprietà.

Per applicare la logica di ripetizione dei tentativi, seguire questa procedura prima di eseguire il comando:

1. Definire i parametri di configurazione usando SqlRetryLogicOption il tipo.
2. Creare un SqlRetryLogicBaseProvider oggetto usando uno dei metodi statici seguenti della SqlConfigurableRetryFactory classe:
   • CreateFixedRetryProvider
   • CreateIncrementalRetryProvider
   • CreateExponentialRetryProvider
   • CreateNoneRetryProvider
3. Assegnare l'oggetto SqlRetryLogicBaseProvider alla RetryLogicProvider proprietà .

Esempio

Nell'esempio seguente viene creato un database e viene stabilita una connessione attiva. Mentre il database ha una connessione attiva, tenta di eliminarlo con un nuovo SqlConnection e un SqlCommand oggetto che usa un SqlRetryLogicBaseProvideroggetto . È necessario eliminare la connessione attiva tramite il database per sbloccare il secondo comando prima di superare il numero di tentativi.
La connessione di blocco simula una situazione come un comando ancora in esecuzione nel database e improbabile che venga completata.

/// 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.

    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}";
    private const string CreateDatabaseFormat = "CREATE 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),
            AuthorizedSqlCondition = null,
            // error number 3702 : Cannot drop database "xxx" because it is currently in use.
            TransientErrors = new int[] {3702}
        };

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

        // define the retrying event to report 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 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 a general connection.
        s_generalConnection.Open();

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

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

    private static void FindActiveSessions(SqlConnection cnn, string dbName)
    {
        using var cmd = cnn.CreateCommand();
        cmd.CommandText = "DECLARE @query NVARCHAR(max) = '';" + Environment.NewLine +
            $"SELECT @query = @query + 'KILL ' + CAST(spid as varchar(50)) + ';' FROM sys.sysprocesses WHERE dbid = DB_ID('{dbName}')" + Environment.NewLine +
            "SELECT @query AS Active_sessions;";
        var reader = cmd.ExecuteReader();
        if (reader.Read())
        {
            Console.ForegroundColor = ConsoleColor.Green;
            Console.Write($">> Execute the '{reader.GetString(0)}' command in SQL Server to unblock the running task.");
            Console.ResetColor();
        }
        reader.Close();
    }

Come usare con i comandi sincroni

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

    // Subscribe a new event on retry event and discover the active sessions on a database
    EventHandler<SqlRetryingEventArgs> retryEvent = (object s, SqlRetryingEventArgs e) =>
    {
        // Run just at first execution
        if (e.RetryCount == 1)
        {
            FindActiveSessions(s_generalConnection, dbName);
            Console.WriteLine($"Before exceeding {provider.RetryLogic.NumberOfTries} attempts.");
        }
    };

    provider.Retrying += retryEvent;

    // Create a new database.
    ExecuteCommand(s_generalConnection, string.Format(CreateDatabaseFormat, dbName));
    Console.WriteLine($"The '{dbName}' database is created.");

    // Open a connection to the newly created database to block it from being dropped.
    using var blockingCnn = new SqlConnection(string.Format(CnnStringFormat, dbName));
    blockingCnn.Open();
    Console.WriteLine($"Established a connection to '{dbName}' to block it from being dropped.");

    Console.WriteLine($"Dropping `{dbName}`...");
    // Try to drop the new database.
    RetryCommandSync(provider, dbName);

    Console.WriteLine("Command executed successfully.");

    provider.Retrying -= retryEvent;
}

private static void RetryCommandSync(SqlRetryLogicBaseProvider provider, string dbName)
{
    using var cmd = s_generalConnection.CreateCommand();
    cmd.CommandText = string.Format(DropDatabaseFormat, dbName);
    // 3. Assign the `provider` to the command
    cmd.RetryLogicProvider = provider;
    Console.WriteLine("The first attempt, before getting into the retry logic.");
    cmd.ExecuteNonQuery();
}

Come usare con comandi asincroni

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

    // Subscribe to the retry event and discover active sessions in a database
    EventHandler<SqlRetryingEventArgs> retryEvent = (object s, SqlRetryingEventArgs e) =>
    {
        // Run just at first execution
        if (e.RetryCount == 1)
        {
            FindActiveSessions(s_generalConnection, dbName);
            Console.WriteLine($"Before exceeding {provider.RetryLogic.NumberOfTries} attempts.");
        }
    };

    provider.Retrying += retryEvent;

    // Create a new database.
    ExecuteCommand(s_generalConnection, string.Format(CreateDatabaseFormat, dbName));
    Console.WriteLine($"The '{dbName}' database is created.");

    // Open a connection to the newly created database to block it from being dropped.
    using var blockingCnn = new SqlConnection(string.Format(CnnStringFormat, dbName));
    blockingCnn.Open();
    Console.WriteLine($"Established a connection to '{dbName}' to block it from being dropped.");

    Console.WriteLine("Dropping the database...");
    // Try to drop the new database.
    RetryCommandAsync(provider, dbName).Wait();

    Console.WriteLine("Command executed successfully.");

    provider.Retrying -= retryEvent;
}

private static async Task RetryCommandAsync(SqlRetryLogicBaseProvider provider, string dbName)
{
    using var cmd = s_generalConnection.CreateCommand();
    cmd.CommandText = string.Format(DropDatabaseFormat, dbName);
    // 3. Assign the `provider` to the command
    cmd.RetryLogicProvider = provider;
    Console.WriteLine("The first attempt, before getting into the retry logic.");
    await cmd.ExecuteNonQueryAsync();
}

Come usare con i comandi asincroni legacy

Oltre a assegnare il provider al comando ed eseguire il comando, è possibile eseguirlo direttamente usando i metodi seguenti SqlRetryLogicBaseProvider :

• Execute<TResult>(Object, Func<TResult>)
• ExecuteAsync(Object, Func<Task>, CancellationToken)
• ExecuteAsync<TResult>(Object, Func<Task<TResult>>, CancellationToken)

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

    // Subscribe to the retry event and discover the active sessions in a database
    EventHandler<SqlRetryingEventArgs> retryEvent = (object s, SqlRetryingEventArgs e) =>
    {
        // Run just at first execution
        if (e.RetryCount == 1)
        {
            FindActiveSessions(s_generalConnection, dbName);
            Console.WriteLine($"Before exceeding {provider.RetryLogic.NumberOfTries} attempts.");
        }
    };

    provider.Retrying += retryEvent;

    // Create a new database.
    ExecuteCommand(s_generalConnection, string.Format(CreateDatabaseFormat, dbName));
    Console.WriteLine($"The '{dbName}' database is created.");

    // Open a connection to the newly created database to block it from being dropped.
    using var blockingCnn = new SqlConnection(string.Format(CnnStringFormat, dbName));
    blockingCnn.Open();
    Console.WriteLine($"Established a connection to '{dbName}' to block it from being dropped.");

    Console.WriteLine("Dropping the database...");
    // Try to drop the new database.
    RetryCommandBeginExecuteAsync(provider, dbName).Wait();

    Console.WriteLine("Command executed successfully.");

    provider.Retrying -= retryEvent;
}

private static async Task RetryCommandBeginExecuteAsync(SqlRetryLogicBaseProvider provider, string dbName)
{
    using var cmd = s_generalConnection.CreateCommand();
    cmd.CommandText = string.Format(DropDatabaseFormat, dbName);
    // Execute the BeginExecuteXXX and EndExecuteXXX functions by using Task.Factory.FromAsync().
    // Apply the retry logic by using the ExecuteAsync function of the configurable retry logic provider.
    Console.WriteLine("The first attempt, before getting into the retry logic.");
    await provider.ExecuteAsync(cmd, () => Task.Factory.FromAsync(cmd.BeginExecuteNonQuery(), cmd.EndExecuteNonQuery));
}

Si applica a