topic Re: SelectionChanged event not firing in ArcObjects SDK Questions

SelectionChanged event not firing

DavidStefan — Sat, 11 Dec 2021 22:58:25 GMT

I want to bind an action to the SelectionChanged event on the map. In the extension, I bind the action to the focused map's SelectionChanged event upon firing ArcMap.Events.NewDocument and ArcMap.Events.NewDocument. The assumption I'm making here is that upon firing of the New(Open)Document events, there is an active document with a map so I can indeed bind actions to its events. But it doesn't work.

What is the correct way of getting this to work?

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using ESRI.ArcGIS.ArcMapUI;
using ESRI.ArcGIS.Carto;

namespace BaseAddin {

    public class BaseExt: ESRI.ArcGIS.Desktop.AddIns.Extension {

        public BaseExt() {
        }

        protected override void OnStartup() {
            WireUpEvents();
        }

        private void WireUpEvents() {
            ArcMap.Events.NewDocument += ArcMap_NewOpenDocument;
            ArcMap.Events.OpenDocument += ArcMap_NewOpenDocument;
        }

        private void ArcMap_NewOpenDocument() {

            IMxDocument doc = ArcMap.Document as IMxDocument;

            ((IActiveViewEvents_Event)doc.FocusMap).SelectionChanged +=
                new IActiveViewEvents_SelectionChangedEventHandler(delegate() {
                    System.Windows.Forms.MessageBox.Show("Feature selection changed.");
            });
        }
    }
}

Re: SelectionChanged event not firing

AlexanderNohe1 — Sat, 11 Dec 2021 22:58:28 GMT

Hi David,

It looks above that you are trying to fire the method. I was able to get this to work by doing the following:

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Windows.Forms;
using ESRI.ArcGIS.ArcMapUI;
using ESRI.ArcGIS.Framework;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Carto;


namespace selChanged
{
    public class Extension1 : ESRI.ArcGIS.Desktop.AddIns.Extension
    {


        private static IActiveViewEvents_Event Events { get { return ArcMap.Document.ActiveView as IActiveViewEvents_Event; } }


        public Extension1()
        {
        }


        protected override void OnStartup()
        {
            Events.SelectionChanged += Events_SelectionChanged;


        }


        void Events_SelectionChanged()
        {
            MessageBox.Show("Selection Changed");
        }




    }


}

Let me know if this works for you

Thanks

Re: SelectionChanged event not firing

DavidStefan — Sat, 11 Dec 2021 22:58:31 GMT

Sadly, this code crashes my ArcMap. In particular, line 28:

Events.SelectionChanged += Events_SelectionChanged;

doesn't allow ArcMap to start and instead displays a dialogue with "ArcGIS Desktop has encountered a serious application error and is unable to continue."

Changing the code to

((IActiveViewEvents_Event)ArcMap.Document.ActiveView).SelectionChanged += delegate() {
                MessageBox.Show("Selection Changed");
            };

results in the same error.

I am running ArcGIS Desktop 10.1 and matching Arcobjects .NET SDK.

Re: SelectionChanged event not firing

AlexanderNohe1 — Mon, 01 Jun 2015 18:27:22 GMT

What I wrote works for me at 10.3. I might be able to test on 10.1 a little later today. Do you have any service packs installed or any other components installed?

Re: SelectionChanged event not firing

DavidStefan — Mon, 01 Jun 2015 19:37:15 GMT

No, it's should be a clean 10.1 install. I've also deleted all other add-ins so the only extension added is the one I'm testing.

Thanks for your help, by the way. I've been pulling my hair over this for two days!

Re: SelectionChanged event not firing

AlexanderNohe1 — Mon, 01 Jun 2015 20:38:41 GMT

I can't reproduce with a clean 10.1 install using the same code provided to you earlier.

Re: SelectionChanged event not firing

DavidStefan — Mon, 01 Jun 2015 20:45:58 GMT

Update: Changing target framework form 4.0 to 3.5 resolves the error described above, but I still do NOT get the message to show upon selecting features...

Re: SelectionChanged event not firing

DavidStefan — Mon, 01 Jun 2015 21:06:03 GMT

I've just changed the extension setting from autoLoad="true" to autoLoad="false". Now when I open ArcMap, then go to Customize -> Extensions and select "Base Extension" it works as expected.

However, when I close and re-open the app, the behaviour falls back to not firing the SelectionChanged event (or, as I imagine, not binding the event to the desired action).

Re: SelectionChanged event not firing

AlexanderNohe1 — Mon, 01 Jun 2015 21:23:48 GMT

Is the extension still checked on in the extensions menu when you reload the app?

Re: SelectionChanged event not firing

DavidStefan — Sat, 11 Dec 2021 22:58:34 GMT

After much trial and error, I have figured out how to solve this. My extension is configured to load automatically upon ArcMap startup and I must bind my action to the SelectionChanged on Document.ActiveView only after the ArcMap.Events.OpenDocument or ArcMap.Events.NewDocument have been fired. This will ensure that the document is ready to accept event bindings. See code below for an illustration.

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Windows.Forms;
using ESRI.ArcGIS.Framework;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Carto;

namespace BaseAddin {

    public class BaseExt: ESRI.ArcGIS.Desktop.AddIns.Extension {

        private static IActiveViewEvents_Event ViewEvents {
            get { return ArcMap.Document.ActiveView as IActiveViewEvents_Event; }
        }

        public BaseExt() {
        }


        protected override void OnStartup() {

            ArcMap.Events.OpenDocument += delegate() {
                ViewEvents.SelectionChanged += SelectionChanged_Handler;
            };

            ArcMap.Events.NewDocument += delegate() {
                ViewEvents.SelectionChanged += SelectionChanged_Handler;
            };
        }

        private void SelectionChanged_Handler() {
            MessageBox.Show("SelectionChanged");
        }
    }
}

Re: SelectionChanged event not firing

DavidStefan — Mon, 01 Jun 2015 21:54:12 GMT

Yes it is. And getting to this point has helped me solve this! I finally figured I have to listen to ArcMap.Events.OpenDocument and bind the SelectionChanged only after the former has been fired. Thanks for you help, my final answer shows the working code.

Re: SelectionChanged event not firing

AlexanderNohe1 — Mon, 01 Jun 2015 22:18:55 GMT

Great! I am glad you got it working!

Re: SelectionChanged event not firing

ChrisBrannin — Sat, 11 Dec 2021 22:58:36 GMT

Any reason this wouldn't work with ItemAdded/ItemRemoved?

private static IActiveViewEvents_Event Events 
        { 
            get { return ArcMap.Document.ActiveView as IActiveViewEvents_Event; } 
        }

void Event_OnOpenDoc()
        {
            ArcMap.Events.OpenDocument += delegate() { Events.ItemAdded += Events_ItemAdded; };
        }

private void Events_ItemAdded(Object item)
        {
            MessageBox.Show("ItemAdded");
        }

I am able to run this without error but nothing happens when an item is added to the view. I feel like I'm missing something or using this incorrectly. Any help with this is greatly appreciated!