need explanation C# below code

siva nathan

5y911Visual Basic .NET

Hi All,

can anyone explain why we use continuewith in C#

return await Task.Run(() =>

{

using (sample d=new sample())

{

classa obj=new classa();

obj.name=a.name;

obj.address=a.address;

return d.create().continuewith((b)=>

return 'welcome';

) ;

}

why we use create.continuewith and why we write inside Task.Run()

can anyone explain the above code

3 Replies

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Mageshwaran R5y ago
Hi Siva,
Asynchronous programming is very popular with the help of the async and await keywords in C#. When we are dealing with UI and on button click, we use a long running method like reading a large file or something else which will take a long time, in that case, the entire application must wait to complete the whole task. In other words, if any process is blocked in a synchronous application, the entire application gets blocked and our application stops responding until the whole task completes.
Asynchronous programming is very helpful in this condition. By using Asynchronous programming, the Application can continue with the other work that does not depend on the completion of the whole task.
Suppose, we are using two methods as Method1 and Method2 respectively and both the methods are not dependent on each other and Method1 is taking a long time to complete its task. In Synchronous programming, it will execute the first Method1 and it will wait for completion of this method and then it will execute Method2. Thus, it will be a time intensive process even though both the methods are not depending on each other
We can run all the methods parallelly by using the simple thread programming but it will block UI and wait to complete all the tasks. To come out of this problem, we have to write too many codes in traditional programming but if we will simply use the async and await keywords, then we will get the solutions in much less code.

Example:
Example:
public class MasterClass
{
    static void Main(string[] args)
    {
        Method1();
        Method2();
        Console.ReadKey();
    }

    public static async Task Method1()
    {
        await Task.Run(() =>
        {
            for (int i = 0; i < 100; i++)
            {
                Console.WriteLine(" Method 1");
            }
        });
    }


    public static void Method2()
    {
        for (int i = 0; i < 25; i++)
        {
            Console.WriteLine(" Method 2");
        }
    }
}
0
Sachin Singh5y ago
sometimes it becomes necessary to invoke a second operation on completion of one task.then we use ContinuWith,
Continuations allow decedent operations to consume the results of the first operation.
and i think your create() should take obj as parameter as it is adding an object to the collection perhaps,
however, as you have used await your UI will not block means the flow will move to the next operation below your whole await task and when it will complete the next task that is welcome will be returned.
0
Amit Gupta5y ago
In Asynchronous programming, ContinueWith is a chaining method that will invoke when the task is completed, in your case it will return "welcome" string.

Know more at
https://docs.microsoft.com/en-us/dotnet/standard/parallel-programming/chaining-tasks-by-using-continuation-tasks
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