Microsoft.Practices.EnterpriseLibrary.TransientFaultHandling.RetryPolicy“返回”对象

Question

我正在使用TransientFaultHandling.RetryPolicy做一些概念验证。

在下面的代码中，我将返回一个数据集。 注意“ return returnDs;” 代码位于ExecuteAction块中。

    public DataSet GetADataSet()
    {
        DataSet returnDs = null;

        RetryStrategy retryStrat = new Incremental(3, TimeSpan.FromMilliseconds(500), TimeSpan.FromSeconds(1));
        RetryPolicy retryPol = new RetryPolicy<SqlDatabaseTransientErrorDetectionStrategy>(retryStrat);

        retryPol.ExecuteAction(() =>
        {

                DatabaseProviderFactory factory = new DatabaseProviderFactory();
                Database db = factory.CreateDefault();
                DbCommand dbc = db.GetStoredProcCommand("dbo.uspGetSomeStuff");
                returnDs = db.ExecuteDataSet(dbc);
                return returnDs;

        });

        throw new InvalidOperationException("RetryPolicy let us down");
    }

代码运行时，可以正确创建returnDs，而不会出现错误，但是会创建“ return returnDs;”。 代码不会退出该过程。 并且InvalidOperationException仍然被执行/抛出。

...

下面的代码可以变通。

    public DataSet GetADataSet()
    {
        DataSet returnDs = null;

        RetryStrategy retryStrat = new Incremental(3, TimeSpan.FromMilliseconds(500), TimeSpan.FromSeconds(1));
        RetryPolicy retryPol = new RetryPolicy<SqlDatabaseTransientErrorDetectionStrategy>(retryStrat);

        retryPol.ExecuteAction(() =>
        {

                DatabaseProviderFactory factory = new DatabaseProviderFactory();
                Database db = factory.CreateDefault();
                DbCommand dbc = db.GetStoredProcCommand("dbo.uspGetSomeStuff");
                returnDs = db.ExecuteDataSet(dbc);

        });

        if (null != returnDs)
        {
            return returnDs;
        }

        throw new InvalidOperationException("RetryPolicy let us down");
    }

......

但是，如果我有一个如下所示的“ void”方法，则没有任何要检查null的东西。

    public void DoSomething()
    {
        DataSet returnDs = null;

        RetryStrategy retryStrat = new Incremental(3, TimeSpan.FromMilliseconds(500), TimeSpan.FromSeconds(1));
        RetryPolicy retryPol = new RetryPolicy<SqlDatabaseTransientErrorDetectionStrategy>(retryStrat);

        retryPol.ExecuteAction(() =>
        {

                DatabaseProviderFactory factory = new DatabaseProviderFactory();
                Database db = factory.CreateDefault();
                DbCommand dbc = db.GetStoredProcCommand("dbo.uspDoSomething");
                db.ExecuteNonQuery(dbc);

        });

        throw new InvalidOperationException("RetryPolicy let us down");
    }

问题1：为什么要“返回returnDs”； 代码不退出程序？

问题2：我的问题是，如何正确使用RetryPolicy，这样，如果所有重试均失败，则可以引发异常。 特别是在“ void DoSomething”方法的情况下。

我可能忽略了这件事。

仅供参考，packages.config

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="CommonServiceLocator" version="1.0" targetFramework="net40" />
  <package id="EnterpriseLibrary.Common" version="6.0.1304.0" targetFramework="net45" />
  <package id="EnterpriseLibrary.Data" version="6.0.1304.0" targetFramework="net45" />
  <package id="EnterpriseLibrary.TransientFaultHandling" version="6.0.1304.0" targetFramework="net45" />
  <package id="EnterpriseLibrary.TransientFaultHandling.Data" version="6.0.1304.1" targetFramework="net45" />
  <package id="Unity" version="2.1.505.0" targetFramework="net40" />
  <package id="Unity.Interception" version="2.1.505.0" targetFramework="net40" />
</packages>

Answer 1

我想到了。

我没有意识到ExecuteAction将基于其中的代码具有返回类型。

    public DataSet GetADataSet()
    {
        DataSet returnDs = null;

        var retryStrategy = new Incremental(3, TimeSpan.FromMilliseconds(500), TimeSpan.FromSeconds(1));
        var retryPolicy = new RetryPolicy<SqlDatabaseTransientErrorDetectionStrategy>(retryStrategy);

        returnDs = retryPolicy.ExecuteAction(() =>
        {
            try
            {
                DatabaseProviderFactory factory = new DatabaseProviderFactory();
                Database db = factory.CreateDefault();
                DbCommand dbc = db.GetStoredProcCommand("dbo.uspGetSomeStuff");

                DataSet ds;
                ds = db.ExecuteDataSet(dbc);
                return ds;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        });

        return returnDs;
    }

和

    public void DoSomething()
    {
        RetryStrategy retryStrat = new Incremental(3, TimeSpan.FromMilliseconds(500), TimeSpan.FromSeconds(1));
        RetryPolicy retryPol = new RetryPolicy<SqlDatabaseTransientErrorDetectionStrategy>(retryStrat);

        int myValue = retryPol.ExecuteAction(() =>
        {
            try
            {
                DatabaseProviderFactory factory = new DatabaseProviderFactory();
                Database db = factory.CreateDefault();
                DbCommand dbc = db.GetStoredProcCommand("dbo.uspDoSomething");
                return db.ExecuteNonQuery(dbc); /* because this returns an int, ExecuteAction return will also be an int */
            }
            catch (Exception ex)
            {
                throw ex;
            }
        });

    }