2 drag n drop events on the same user control using MVVM and Gong WPF Drag n Drop library
I'm trying to handle 2 different drag events using the gong-wpf-dragdrop library and MVVM.
First, we drag n drop a file onto the window to load the data.
Second, we drag rows to reorder a DataGrid.
I have no problem getting one OR the other to work. However, when I apply both they conflict with each other.
e.g. I drag a json file onto the form and it de-serializes the object into the form. The object has a list represented with a DataGrid. When I drag a row to reorder them, it triggers my load file method and throws an exception because the data type is wrong.
How can I separate the 2 events so that my reorder drag does not call the file drop method? This is easy with traditional code behind but I'm having difficulty doing this with MVVM and the gong library.
Here are some excerpts from the code. (only relevant parts shown for brevity)
Thanks in advance for any insight you can offer. I'm sure it's something silly.
MyUserControl.xaml
<UserControl x:Class="MyEditor.Views.MyEditor"
xmlns:dd="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"
<!-- This enables the file drop -->
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}">
<UserControl.DataContext>
<local:MyViewModel/>
</UserControl.DataContext>
<Grid>
<DataGrid x:Name="MyKeyValueList"
<!-- This enables the row reorder -->
dd:DragDrop.DropScrollingMode="VerticalOnly"
dd:DragDrop.IsDragSource="True"
dd:DragDrop.IsDropTarget="True">
...
</DataGrid>
</Grid>
MyViewModel.cs
// How do I get this to only get called for a file drop?
public void DragOver(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>(); // Throws System.InvalidCastException as expected when reordering the DataGrid rows.
dropInfo.DropTargetAdorner = DropTargetAdorners.Insert;
dropInfo.Effects = DragDropEffects.Copy;
}
// Same issue. How do I get this to only get called for a file drop?
public void Drop(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>();
dropInfo.Effects = dragFileList.Any(item =>
{
Settings = Services.FileServices.ReadFileToSetting(item);
return true;
}) ? DragDropEffects.Copy : DragDropEffects.None;
}
c# wpf mvvm drag-and-drop
asked Nov 23 at 3:25
Gary Elliott
11
add a comment |
I'm trying to handle 2 different drag events using the gong-wpf-dragdrop library and MVVM.
First, we drag n drop a file onto the window to load the data.
Second, we drag rows to reorder a DataGrid.
I have no problem getting one OR the other to work. However, when I apply both they conflict with each other.
e.g. I drag a json file onto the form and it de-serializes the object into the form. The object has a list represented with a DataGrid. When I drag a row to reorder them, it triggers my load file method and throws an exception because the data type is wrong.
How can I separate the 2 events so that my reorder drag does not call the file drop method? This is easy with traditional code behind but I'm having difficulty doing this with MVVM and the gong library.
Here are some excerpts from the code. (only relevant parts shown for brevity)
Thanks in advance for any insight you can offer. I'm sure it's something silly.
MyUserControl.xaml
<UserControl x:Class="MyEditor.Views.MyEditor"
xmlns:dd="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"
<!-- This enables the file drop -->
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}">
<UserControl.DataContext>
<local:MyViewModel/>
</UserControl.DataContext>
<Grid>
<DataGrid x:Name="MyKeyValueList"
<!-- This enables the row reorder -->
dd:DragDrop.DropScrollingMode="VerticalOnly"
dd:DragDrop.IsDragSource="True"
dd:DragDrop.IsDropTarget="True">
...
</DataGrid>
</Grid>
MyViewModel.cs
// How do I get this to only get called for a file drop?
public void DragOver(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>(); // Throws System.InvalidCastException as expected when reordering the DataGrid rows.
dropInfo.DropTargetAdorner = DropTargetAdorners.Insert;
dropInfo.Effects = DragDropEffects.Copy;
}
// Same issue. How do I get this to only get called for a file drop?
public void Drop(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>();
dropInfo.Effects = dragFileList.Any(item =>
{
Settings = Services.FileServices.ReadFileToSetting(item);
return true;
}) ? DragDropEffects.Copy : DragDropEffects.None;
}
c# wpf mvvm drag-and-drop
asked Nov 23 at 3:25
Gary Elliott
11
Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28
add a comment |
I'm trying to handle 2 different drag events using the gong-wpf-dragdrop library and MVVM.
First, we drag n drop a file onto the window to load the data.
Second, we drag rows to reorder a DataGrid.
I have no problem getting one OR the other to work. However, when I apply both they conflict with each other.
e.g. I drag a json file onto the form and it de-serializes the object into the form. The object has a list represented with a DataGrid. When I drag a row to reorder them, it triggers my load file method and throws an exception because the data type is wrong.
How can I separate the 2 events so that my reorder drag does not call the file drop method? This is easy with traditional code behind but I'm having difficulty doing this with MVVM and the gong library.
Here are some excerpts from the code. (only relevant parts shown for brevity)
Thanks in advance for any insight you can offer. I'm sure it's something silly.
MyUserControl.xaml
<UserControl x:Class="MyEditor.Views.MyEditor"
xmlns:dd="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"
<!-- This enables the file drop -->
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}">
<UserControl.DataContext>
<local:MyViewModel/>
</UserControl.DataContext>
<Grid>
<DataGrid x:Name="MyKeyValueList"
<!-- This enables the row reorder -->
dd:DragDrop.DropScrollingMode="VerticalOnly"
dd:DragDrop.IsDragSource="True"
dd:DragDrop.IsDropTarget="True">
...
</DataGrid>
</Grid>
MyViewModel.cs
// How do I get this to only get called for a file drop?
public void DragOver(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>(); // Throws System.InvalidCastException as expected when reordering the DataGrid rows.
dropInfo.DropTargetAdorner = DropTargetAdorners.Insert;
dropInfo.Effects = DragDropEffects.Copy;
}
// Same issue. How do I get this to only get called for a file drop?
public void Drop(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>();
dropInfo.Effects = dragFileList.Any(item =>
{
Settings = Services.FileServices.ReadFileToSetting(item);
return true;
}) ? DragDropEffects.Copy : DragDropEffects.None;
}
c# wpf mvvm drag-and-drop
asked Nov 23 at 3:25
Gary Elliott
11
I'm trying to handle 2 different drag events using the gong-wpf-dragdrop library and MVVM.
First, we drag n drop a file onto the window to load the data.
Second, we drag rows to reorder a DataGrid.
I have no problem getting one OR the other to work. However, when I apply both they conflict with each other.
e.g. I drag a json file onto the form and it de-serializes the object into the form. The object has a list represented with a DataGrid. When I drag a row to reorder them, it triggers my load file method and throws an exception because the data type is wrong.
How can I separate the 2 events so that my reorder drag does not call the file drop method? This is easy with traditional code behind but I'm having difficulty doing this with MVVM and the gong library.
Here are some excerpts from the code. (only relevant parts shown for brevity)
Thanks in advance for any insight you can offer. I'm sure it's something silly.
MyUserControl.xaml
<UserControl x:Class="MyEditor.Views.MyEditor"
xmlns:dd="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"
<!-- This enables the file drop -->
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}">
<UserControl.DataContext>
<local:MyViewModel/>
</UserControl.DataContext>
<Grid>
<DataGrid x:Name="MyKeyValueList"
<!-- This enables the row reorder -->
dd:DragDrop.DropScrollingMode="VerticalOnly"
dd:DragDrop.IsDragSource="True"
dd:DragDrop.IsDropTarget="True">
...
</DataGrid>
</Grid>
MyViewModel.cs
// How do I get this to only get called for a file drop?
public void DragOver(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>(); // Throws System.InvalidCastException as expected when reordering the DataGrid rows.
dropInfo.DropTargetAdorner = DropTargetAdorners.Insert;
dropInfo.Effects = DragDropEffects.Copy;
}
// Same issue. How do I get this to only get called for a file drop?
public void Drop(IDropInfo dropInfo)
{
var dragFileList = ((DataObject)dropInfo.Data).GetFileDropList().Cast<string>();
dropInfo.Effects = dragFileList.Any(item =>
{
Settings = Services.FileServices.ReadFileToSetting(item);
return true;
}) ? DragDropEffects.Copy : DragDropEffects.None;
}
c# wpf mvvm drag-and-drop
c# wpf mvvm drag-and-drop
asked Nov 23 at 3:25
Gary Elliott
11
asked Nov 23 at 3:25
Gary Elliott
11
asked Nov 23 at 3:25
Gary Elliott
11
asked Nov 23 at 3:25
Gary Elliott
11
asked Nov 23 at 3:25
Gary Elliott
11
11
Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28
add a comment |
Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28
Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28
add a comment |
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Instead of casting directly you can first check the data type is correct and then do the cast. If data type is not what you expect, just return from the method without handling the event and DataGrid should handle it afterwards.
– Yusuf Tarık Günaydın
Nov 23 at 7:43
Thanks for the suggestion Yusuf. I did consider that but it seems there should be a way to call the correct method in the first place.
– Gary Elliott
Nov 23 at 21:28