Async for Bulk copy

问题:

I have quite a few datatable to bulkinsert into databasetable Due to large size, one table took 5 min to complete insert. 2 tables took me 10 min

static void Main(string[] args) {     DataTableBulkInsert(DataTable1);     DataTableBulkInsert(DataTable2); }  public static void DataTableBulkInsert(DataTable Table){     SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(myConnection);     sqlBulkCopy.DestinationTableName = "dbo.DatabaseTable";     myConnection.Open();                         sqlBulkCopy.WriteToServer(Table);     myConnection.Close(); } 

I am now trying to do a async for Bulk insert, but there is neither any data inserted nor giving me error. How to capture the exception?

static void Main(string[] args) {      var insert1 = Task.Run(async () => await DataTableBulkInsert(DataTable1);      var insert2 = Task.Run(async () => await DataTableBulkInsert(DataTable2);      Task.WhenAll( insert1, insert 2); }  public static async Task<Boolean> DataTableBulkInsert(DataTable Table) {       try       {           SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(myConnection);           sqlBulkCopy.DestinationTableName = "dbo.DatabaseTable";           myConnection.Open();                               await sqlBulkCopy.WriteToServerAsync(Table);           myConnection.Close();       }       catch (Exception (e))       {         console.write(e);       }       return true;  } 

回答1:

The Task.Runs are adding nothing useful here. Also, don't try to share a single connection object between the two runs of your method. Something like:

static void Main(string[] args) {      var insert1 = DataTableBulkInsert(DataTable1);      var insert2 = DataTableBulkInsert(DataTable2);      Task.WaitAll( insert1, insert2); }  public static async Task DataTableBulkInsert(DataTable Table) {       using(var localConnection = new SqlConnection(/* connection string */))       {           SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(localConnection );           sqlBulkCopy.DestinationTableName = "dbo.DatabaseTable";           localConnection.Open();                               await sqlBulkCopy.WriteToServerAsync(Table);       }  } 

Normally return await is an anti-pattern, but here you want to use it so that the using statement doesn't close your connection until after the bulk load is complete.

Also, I switched to using Task.WaitAll which actually waits, which is more idiomatic than using Task.WhenAll and then immediately calling Wait on it.

回答2:

Task.WhenAll returns a Task object that needs to be awaited or the code that follows continues its normal execution and the main method exits immediately.

Since this is a console application and the main can't be marked as async, you can use this:

Task.WhenAll(insert1, insert2).Wait(); // wait for the returned Task object to Complete 

The normal usage is: await (Task.WhenAll(...)) but you can't mark Main as an async method.

文章来源: Async for Bulk copy