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This article mainly introduces how to use VB.NET in database programming, which is very detailed and has certain reference value. Friends who are interested must finish reading it.

Threads are the basic unit in which the operating system allocates processor time. Threads can run multiple activities while a single thread executes. Operating systems that support preemptive multitasking can create multiple threads and make them run at the same time through time slice rotation. In applications that require good user interaction and applications that communicate with networks and databases, the use of multithreading can provide a good interactive experience and respond quickly to the requirements of users. This paper mainly introduces the specific application of threads in .NET in database programming (realized by VB.NET).

1 create a database access thread

In database applications, especially network database access, because a large amount of data may be accessed, it takes a long time to get results, and a good program should have good interactivity. when accessing the database, you should allow your application to respond to the user's activities as soon as possible to provide a rich user experience. The use of multi-threading mechanism allows a lot of time-consuming operations to run in the background in order to quickly respond to the activities of users. The following code accesses the database and returns the data table:

Private sub GetDataFromDataBase ()... M_table.Clear () m_sqlDataAdapter.Fill (m_table)... End Sub

To create a new instance of the Thread object, you need to create a new thread agent. The ThreadStart thread agent can specify the name of the method to execute when the thread is generated, but the thread agent does not actually run the thread. When you create a ThreadStart object, you specify a pointer to the method to run when the thread starts execution, which cannot accept any parameters. Let's assign the above code to a thread and start it:

Dim myThreadStart as ThreadStart = New ThreadStart (AddressOf GetDataFromDataBase) Dim myThread as Thread=New Thread (myThreadStart) myThread.Start ()

In this way, when accessing the database, the user can continue to process.

The 2.VB.NET thread method uses events

Calling the thread's start method does not guarantee that the method is executed immediately, and you must wait for the method to finish executing in order to get the result of data access. If the use of a circular query after running a thread obviously affects interactivity, events are a good way to return data from a thread method. Simply define an event in the class where the VB.NET thread method is located, emit the event in the VB.NET thread method, and generate a proxy in the form class.

First, add the event after the dealDataBase class declaration:

Public Class dealDataBase Public Event GetDataComplete (ByVal e As DtatTable) … End Class

Add the code that emits the event in the GetDataFromDataBase () method of class dealDataBase, and put it after m_sqlDataAdapter.Fill (m_table):

Public sub GetDataFromDataBase ()... M_sqlDataAdapter.Fill (m_table) RasiseEvent GetDataComplete (m_table)... End Sub

Let's generate a proxy in the form class

Private Sub dealData (ByVal e As DataTable) 'processing datasheet End Sub

Event concatenation is made in the code that creates and runs the thread, the event connection code is placed before the running thread, and after the dealDataBase class is instantiated:

AddHandler myDB. GetDataComplete,AddressOf dealData

In this way, when the thread method finishes executing, the event is emitted, and the dealData method responds to the event and handles it.

These are all the contents of this article entitled "how to use threads in VB.NET database programming". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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