尝试调用方法时无法从 void 转换为 System.Action

Question

I have this code:

    public void UpdateDConfDictionaryToCol(DconF dconF)
    {
        var allDconf = GetDConfFromCol();           
        allDconf[dconF.id.ToString()] = dconF;          
        var serializeJson = Helpers.JsonConverter.SerializeEscapeHtml(allDconf);
        App.CM.UpdateCol(serializeJson,CONST.dconfCol);
    }

I would like to time how long it takes to execute so I am trying to use some code that my application has:

public static partial class Helper
{
    public static string Timer(Action action)
    {
        var stopWatch = Stopwatch.StartNew();
        stopWatch.Start();
        action();
        return stopWatch.ElapsedMilliseconds.ToString();
    }

    public static int TimerInt(Action action)
    {
        var stopWatch = Stopwatch.StartNew();
        stopWatch.Start();
        action();
        return (int) stopWatch.ElapsedMilliseconds;
    }
}

Here is where I am using it:

var abc = Helper.Timer(App.CM.UpdateDConfDictionaryToCol(App.CM.SelectedDconf));

But it gives me an error message saying:

argument 1, cannot convert from void to system Action

Answer 1

You are passing in App.CM.UpdateDConfDictionaryToCol(App.CM.SelectedDconf) to the Helper.Timer . That returns void and gets evaluated to be a parameter to Helper.Timer method. However, Helper.Timer expects an action. This is the reason for the error you are seeing.

You may do the following

// Pass the action as a parameter and invoke this inside the method with the parameter
// The action in this case should be Action<T> where T is DConf
var abc = Helper.Timer(App.CM.UpdateDConfDictionaryToCol);

// invoking the action with the parameter within Helper.Timer
// However, the helper needs to know of the parameter App.CM.UpdateConf separately. Another
// simpler alternative is provided in the second approach below
action(App.CM.UpdateConf);

OR

Always, in general, make sure to pass the delegate ( Action in this case) as shown below and do not pass call to the method directly as that gets evaluated to the return type of the method but not as a delegate as we expect it to be.

var abc = Helper.Timer(() => App.CM.UpdateDConfDictionaryToCol(App.CM.SelectedDconf))