In the group today , Someone asked There are several void Methods to return values , But I want these methods to have execution order , What to do with ,ABCD Four ways , Execute sequentially , But these methods have no return value
The question is very simple , If the method is synchronous , Just write directly in four consecutive ways , such as ：
static void Main()
{
A();
B();
C();
D();
}
But if the method contains time-consuming operations , Then there is a problem with writing four in this way , The execution sequence is wrong , We need to use callback Function to operate , But in line with the idea of not moving the original method , We use Task Of OnCompleted event （.net framework Can be used in BeginInvoke(callback,null)） To deal with
- If the method has a return value , Then use Func, perhaps Func<>
- If the method does not return a value , Then use Action, perhaps Action<>
1. No return value in .net core Use in Task Of OnCompleted event
Because it is a method without return value , We use
for example
static void Main()
{
Action action1 = () => {
Thread.Sleep(1000);
Console.WriteLine("action1");
};
Action action2 = () => {
Thread.Sleep(2000);
Console.WriteLine("action2");
};
Action action3 = () => {
Thread.Sleep(3000);
Console.WriteLine("action3");
};
Action action4 = () => {
Thread.Sleep(3000);
Console.WriteLine("action4");
};
Stack st = new Stack();
st.Push(action2);
st.Push(action3);
st.Push(action4);
void MyAsynCallback()
{
if (st.Count > 0)
{
var action = (Action)st.Pop();
Task.Run(action).GetAwaiter().OnCompleted(() =>
{
MyAsynCallback();
});
}
}
Task.Run(action1).GetAwaiter().OnCompleted(() =>
{
MyAsynCallback();
});
Console.ReadLine();
//Stack Of Pop First in, then out , Output order action1 action4 action3 action2
}
We can Stack Change it to something else , such as List、Queue etc. , Decide whether you need to pop it up manually action that will do
2. No return value in .net framework Use in BeginInvoke
static void Main()
{
Action action1 = () => {
Thread.Sleep(1000);
Console.WriteLine("action1");
};
Action action2 = () => {
Thread.Sleep(2000);
Console.WriteLine("action2");
};
Action action3 = () => {
Thread.Sleep(3000);
Console.WriteLine("action3");
};
Action action4 = () => {
Thread.Sleep(3000);
Console.WriteLine("action4");
};
Stack st = new Stack();
st.Push(action2);
st.Push(action3);
st.Push(action4);
void MyAsynCallback(IAsyncResult async)
{
if (st.Count > 0)
{
var action = (Action)st.Pop();
action.BeginInvoke(new AsyncCallback(MyAsynCallback),null);
}
}
action1.BeginInvoke(new AsyncCallback(MyAsynCallback), null);
Console.ReadLine();
//Stack Of Pop First in, then out , Output order action1 action4 action3 action2
}
3. There is a return value in .net core Use in Task Of OnCompleted event
Because it is a method without return value , We use
for example
static void Main()
{
Func<int> func1 = () => {
Thread.Sleep(1000);
Console.WriteLine("func1");
return 1;
};
Func<int> func2 = () => {
Thread.Sleep(2000);
Console.WriteLine("func2");
return 1;
};
Func<int> func3 = () => {
Thread.Sleep(3000);
Console.WriteLine("func3");
return 0;
};
Func<int> func4 = () => {
Thread.Sleep(3000);
Console.WriteLine("func4");
return 1;
};
Stack st = new Stack();
st.Push(func2);
st.Push(func3);
st.Push(func4);
void MyAsynCallback(int result)
{
if (st.Count > 0 && result > 0)
{
var action = (Func<int>)st.Pop();
var task1 = Task.Run(action);
task1.GetAwaiter().OnCompleted(() =>
{
MyAsynCallback(task1.Result);
});
}
}
var task = Task.Run(func1);
task.GetAwaiter().OnCompleted(() =>
{
MyAsynCallback(task.Result);
});
Console.ReadLine();
//Stack Of Pop First in, then out , Output order func1 func4 func3 func2
}
4. There is a return value in .net framework Use in BeginInvoke
delegate int dele_func(int a);
static void Main()
{
Func<int> func1 = () => {
Thread.Sleep(1000);
Console.WriteLine("func1");
return 1;
};
Func<int> func2 = () => {
Thread.Sleep(2000);
Console.WriteLine("func2");
return 1;
};
Func<int> func3 = () => {
Thread.Sleep(3000);
Console.WriteLine("func3");
return 1;
};
Func<int> func4 = () => {
Thread.Sleep(3000);
Console.WriteLine("func4");
return 1;
};
Stack st = new Stack();
st.Push(func2);
st.Push(func3);
st.Push(func4);
void MyAsynCallback(IAsyncResult async)
{
dele_func dele_Func2 = (dele_func)async.AsyncState;
int result = dele_Func2.EndInvoke(async);
if (st.Count > 0 && result > 0)
{
var action = (Func<int>)st.Pop();
dele_func dele_Func1 = new dele_func((int a) => { return action.Invoke(); });
IAsyncResult asyncResult1 = dele_Func1.BeginInvoke(0, new AsyncCallback(MyAsynCallback), dele_Func1);
}
}
dele_func dele_Func = new dele_func((int a) => { return func1.Invoke(); });
IAsyncResult asyncResult = dele_Func.BeginInvoke(0, new AsyncCallback(MyAsynCallback), dele_Func);
Console.ReadLine();
//Stack Of Pop First in, then out , Output order func1 func4 func3 func2
}
When there is a return value , According to result The judgment of the , To determine whether to proceed
If there is a problem , Welcome to correct
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