c# 7.0: switch on System.Type

Question

No existing question has an answer to this question.

In c# 7, can I switch directly on a System.Type?

When I try:

    switch (Type)         


        

Answer 1

Here is an alternative which won't compile as the classes are missing:

bool? runOnUI = queuedAction.RunOnUI;  // N=null, T=true F=False
bool isOnUI = Statics.CoreDispatcher.HasThreadAccess;
bool isFF = queuedAction.IsFireAndForget;   // just makes it easier to read the switch statement
if (false == queuedAction.IsFireAndForget)
    IsOtherTaskRunning = true;

/* In the case statements below the string name is something like noFF_TN
 * The compiler ignores the string name. I have used them here to represent
 * the logic in the case statement:   ( FF = FireAnd Forget, T=true, F=false, N = null, * means 'whatever')
 * 
 *      isFF_** = FireAndForget QueuedAction
 *      noFF_** = Not FireAndForget so Wait for Task to Finish (as opposed to Complete)
 *      ****_T* = We are already on the UI thread 
 *      ****_F* = We are not on the UI thread 
 *      ****_*T = Run on the UI thread.
 *      ****_*F = Do not run on UI thread
 *      ****_*N = Don't care so run on current thread
 *      
 *  The last character is a "bool?" representing RunOnUI. It has
 *  three values each of which has a different meaning */

bool isTask;
switch ("ignore")
{
    /* Run it as an Action (not Task) on current Thread   */
    case string noFF_TT when !isFF && isOnUI && runOnUI == true:
    case string isFF_TN when isFF && isOnUI && !runOnUI == null:
    case string isFF_FN when isFF && !isOnUI && runOnUI == null:
    case string isFF_TT when isFF && isOnUI && runOnUI == true:
    case string isFF_FF when isFF && !isOnUI && runOnUI == false:
        isTask = false;
        queuedAction.ActionQA(queuedAction); // run as an action, not as a Task
        break;

    /* Create a Task, Start it */

    case string isFF_TF when isFF && isOnUI == true && runOnUI == false:
    case string noFF_TN when !isFF && isOnUI == true && runOnUI == null:     // <== not sure if I should run it on UI instead
    case string noFF_TF when !isFF && isOnUI && runOnUI == false:
    case string noFF_FN when !isFF && !isOnUI && runOnUI == null:
    case string noFF_FF when !isFF && !isOnUI && runOnUI == false:
        var cancellationTokenSource = new CancellationTokenSource();
queuedAction.Canceller?.SetCancellationTokenSource(cancellationTokenSource);
        isTask = true;
        new Task
            (
                (action) => queuedAction.ActionQA(queuedAction),
                queuedAction,
                cancellationTokenSource.Token
            )
            .Start();
        break;

    /* Run on UI and don't wait */

    case string isFF_FT when isFF && !isOnUI && runOnUI == true:
        isTask = true;
        Statics.RunOnUI(() => queuedAction.ActionQA(queuedAction), asTaskAlways: true);
        break;

    /* Run on the UI as a Task and Wait */

    case string noFF_FT when !isFF && !isOnUI && runOnUI == true:
        isTask = true;
        Statics.RunOnUI(() => queuedAction.ActionQA(queuedAction), asTaskAlways: true);
        break;

    default:
        throw new LogicException("unknown case");
}