DevExpress XtraGrid FocusedRowChanged event problem when changing datasource

This problem has bugged me for several years and maybe 开发者_C百科someone here knows a simple solution, since I just ran into it again.

QUESTION: Is there any way to get the XtraGrid to "forget" the current focused row index before a new (different) datasource is assigned to the grid?

BACKGROUND We use the XtraGrid as a kind of controller for what is displayed in another panel of a multipane Winform.

Now imagine a hypothetical scenario where the datasource of the XtraGrid keeps changing according to menu selections. Menu item 1 populates the grid with a list of today's entrees in the cafeteria: Id, Name. Menu item 2 populates the grid with a list of Customers the user must phone that day: ID, Name. Important thing is that these are separate distinct datasources, and the grid's datasource is being assigned and reassigned.

CRITICAL FACT FOR THIS QUESTION: We want the grid's FocusedRowChanged event to be the single place where we trap the user's selection in the controller grid. We are a "no spaghetti code" shop. FocusedRowChanged is better than a click event because it handles keyboard navigation too. The row with the focus contains the ID of the detail record we need to fetch from the database for display in Panel #2. This works--most of the time.

Here's how it doesn't work: let's say that on a given day, the list of customers the user must contact contains only one row. So the first (and only) row in the grid is the focused row. Now let's say that the user goes up to the menu and selects the menu item to display the day's cafeteria entrees. When the user clicks on the first item in the Entrees list, the FocusedRowChanged event does NOT fire because the grid has retained a memory of the focused row index from the previous datasource. The focused row index has not changed. And thus the user's selection doesn't trigger anything.

I tried to get DevExpress to offer a second more row-object-oriented mode (as distinct from row-index-oriented approach) whereby each row in the grid would have a GUID, and the FocusedRowChanged event would fire whenever the GUID of the currently focused row differed from the GUID of the previously focused row, regardless of whether the focused row index happened to be the same. This would allow dynamic changes of datasource and enable the desired behavior. But they demurred.

So I'll ask my question again, Is there any way to get the XtraGrid to "forget" the current focused row index before a new datasource is assigned to the grid?

Tim, I had the exact same problem when the grid only had one row of data in it and then changed data sources. I solved it by setting the gridview.FocusedRowHandle = -1 after setting the new datasource.

In a similar situation, I am subscribing to the

FocusedRowObjectChanged

event (using DevExpress 16.1).

I think that the best solution to this problem is to create a new GridView object and override its DoChangeFocusedRowInternal method. Below you will find the default implementation of this method. All you need to do is to change the marked row just as your needs dictate. Also, take a look at the How to create a GridView descendant class and register it for design-time use article, it contains some useful information.

public class MyGridView : GridView {
        protected override void DoChangeFocusedRowInternal(int newRowHandle, bool updateCurrentRow) {
            if(this.lockFocusedRowChange != 0) return;
            if(!IsValidRowHandle(newRowHandle))
                newRowHandle = DevExpress.Data.DataController.InvalidRow;
            if(FocusedRowHandle == newRowHandle) return; // <<<<<<
            int currentRowHandle = FocusedRowHandle;
            BeginLockFocusedRowChange();
            try {
                DoChangeFocusedRow(FocusedRowHandle, newRowHandle, updateCurrentRow);
            }
            finally {
                EndLockFocusedRowChange();
            }
            RaiseFocusedRowChanged(currentRowHandle, newRowHandle);
        }
    }

UPDATE

My code:

namespace MyXtraGrid {

        public class MyGridControl : GridControl {
            protected override BaseView CreateDefaultView() {
                return CreateView("MyGridView");
            }
            protected override void RegisterAvailableViewsCore(InfoCollection collection) {
                base.RegisterAvailableViewsCore(collection);
                collection.Add(new MyGridViewInfoRegistrator());
            }
        }

        public class MyGridViewInfoRegistrator : GridInfoRegistrator {
            public override string ViewName { get { return "MyGridView"; } }
            public override BaseView CreateView(GridControl grid) {
                return new MyGridView(grid as GridControl);
            }
        }
        public class MyGridView : GridView {
            public MyGridView(GridControl ownerGrid) : base(ownerGrid) { }
            public MyGridView() { }


            protected virtual bool RowEqual(int focusedRowHandle, int newRowHandle) {
                if(IsDesignMode)
                    return focusedRowHandle == newRowHandle;
                DataRow row1 = GetDataRow(focusedRowHandle);
                DataRow row2 = GetDataRow(newRowHandle);
                return row1 == row2;
            }

            protected override void DoChangeFocusedRowInternal(int newRowHandle, bool updateCurrentRow) {
                if(this.lockFocusedRowChange != 0) return;
                if(!IsValidRowHandle(newRowHandle))
                    newRowHandle = DevExpress.Data.DataController.InvalidRow;
                if(RowEqual(FocusedRowHandle, newRowHandle))
                    return;
                int currentRowHandle = FocusedRowHandle;
                BeginLockFocusedRowChange();
                try {
                    DoChangeFocusedRow(FocusedRowHandle, newRowHandle, updateCurrentRow);
                }
                finally {
                    EndLockFocusedRowChange();
                }
                RaiseFocusedRowChanged(currentRowHandle, newRowHandle);
            }
        }
    }

You can subscribe on the DataSourceChanged event which will fire when Data source changes (you guessed it!) so then you can get using GetFocusedObject() the object and display the relevant items for the other grid...