Can't seem to find part/node by key

I have the following code here:

    myDiagram.addDiagramListener("ExternalObjectsDropped", function (e) {
        myDiagram.toolManager.draggingTool.reset();  // remove any guidelines

        var deviceNode = e.diagram.selection.first(); = "myId";            
        if (myDiagram.findNodeForKey("myId")) {
        } else {

Why is it I always get false?

I have tried getNodeForKey and getPartForKey, both yields the same result.

From the documentation for Model, :

[quote]This model cannot detect the modification of the #nodeDataArray array or the modification of any node data object. If you want to add or remove node data from the #nodeDataArray, call the #addNodeData or #removeNodeData methods.

If you want to modify a node data object, it depends on whether the property you want to change is a structural property that the model needs to know about, or whether it is a property that is only used for data binding or other application-specific purposes.

For the former case, call the appropriate method, such as#setKeyForNodeData, #setCategoryForNodeData,GraphLinksModel#setToKeyForLinkData, or GraphLinksModel#setGroupKeyForNodeData. These methods have names that start with “set”, “add”, “insert”, or “remove”.

For the latter case, when setting an application-specific property, typically for data binding, and to support undo/redo, call #setDataProperty.[/quote]