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

Question

I'm doing a little Proof of Concept with TransientFaultHandling.RetryPolicy.

In the below code, I'm returning a dataset. Note the "return returnDs;" code is inside the ExecuteAction block.

    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");
    }

When the code runs, the returnDs is created correctly with no errors, but the "return returnDs;" code does not exit the procedure. And InvalidOperationException still gets executed/thrown.

...

The below code works as a work around.

    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");
    }

......

However, if I have a "void' method as seen below, I don't have anything to check null for.

    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");
    }

Question 1: Why does the "return returnDs;" code not exit the procedure?

Question 2: So my question is, how do I use RetryPolicy correctly, so that if all the retries fail, I can throw an exception. Especially in the case of "void DoSomething" method.

It's probably something stupid I'm overlooking.

FYI, 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

I figured it out.

I didn't realize ExecuteAction will have a return type based on the code within it.

    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;
    }

and

    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;
            }
        });

    }