Execute Long Running SQL Query Or Stored Procedure From .NET

The following 2 main issues arise when your application is intended to deal with huge data-

These issues are some serious issues while building interactive applications. User patience is an unpredictable parameter and the user’s reaction against a long waiting screen is uncertain. At least UI shouldn't be frozen to engage the user and make him wait for the result.

Since transactional SQL statements will definitely take time to process the things, the quickest solution sought is on the application programming level. Also, it is known that MS SQL Server takes each & every call as synchronous, even if you change the connection string property AsynchronousProcessing to true. It is A client application (C#, .net) which gets affected, so the following are some widely used solutions-

It has many limitations, for example, a fired SQL command can be canceled by firing SqlCommand.Cancel() but for this, that command object must persist. SqlReader's Close or Read is designed to ignore this Cancel() call if this call is not placed before them and so on.

It is a great programming style that solves many issues and helps you to build more interactive UI based applications. Instead of holding execution on a long-running statement(s), it allows you to carry on to the next line of code. In this post, we will implement this functionality to execute SQL queries asynchronously.

In our sample project which is a WPF application, we will use the Callback mechanism. Let's add the following controls on the Window-

Idea is to fire asynchronous call to MS SQL for the T-SQL statement written in textboxQuery on the btnExecuteQuery click event.

For executing MS SQL statements in asynchronous, we have to-

At the connection level, a specification is required in the connection string for asynchronous processing.

Example: AsynchronousProcessing = true

At SqlCommand execution level, instead of ExecuteReader() we need to use BeginExecuteReader() and EndExecuteReader() methods to achieve asynchronous execution. BeginExecuteReader takes the following 2 arguments:

Generally, the state-object is the object which will be required in the callback method to process the things. Here, we are passing the SqlCommand object because our SQL query will be executed in different functions inside different worker threads. Our SqlCommand object is already initialized and ready to use by a callback function.

Let’s focus on our callback function, which has been passed to AsyncCallback() inside BeginExecuteReader(). It has the following syntax:

Please note the IAsyncResult type, which is required to hold the status of an asynchronous operation.

To un-box the AsynState back to the SqlCommand, we need to typecast as below-

So far, we understood the required logic. Let's collaborate the things together. Our button click event handler code would look like the following: