ListBox (Multiple Selection) InvalidCastException

Radzen Studio Blazor Server
1

Hello everyone,

I'm having some issues on multiple selection for ListBox component. The necessary code is above.

The component loads correctly with the values but I can't check any item (it doesn't tick when I click)... Also when I click on the square near the search icon (select all) i get the following exception:

System.InvalidCastException: Unable to cast object of type 'System.Collections.Generic.List`1[System.Object]' to type 'System.Collections.Generic.IEnumerable`1[System.String]'.
   at Radzen.Blazor.RadzenListBox`1.SelectAll()
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle)

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<RadzenListBox AllowFiltering="true" FilterCaseSensitivity="FilterCaseSensitivity.CaseInsensitive" TValue="IEnumerable<string>" @bind-Value="multipleLocations" Multiple="true" Data="@locations.ToList()"
                                       Change="@(args => Change(args))" Style="height:200px;" />

IEnumerable<string> multipleLocations = new string[] { };

string[] locations = new string[] { "ex1", "ex2" };

Any tips for this?

Thanks in advance!

2

Hi @svrebelo,

Thanks for the report! It will be fixed in the next update!

1 Like
3

The problem was fixed and new version of Radzen.Blazor was just published. You need to change a bit your code however since currently Data="@locations.ToList()" will cause Data property change on every cycle and the component will unable to maintain the selection.

4

@enchev thank you! Going to upgrade from 2.8.4 to 2.9.1

In that case, how should I bind data? Just want to know, in short, what I'll have to do.

Thanks for your help! Such a Fast fix!

5

Without ToList() is enough:

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image1920×1080 110 KB

1 Like
6

@enchev Working as expected!

Thanks for the support!

7

I've remember one thing!

Applying the Required Validator doesn't seem to work for me. When no items are selecred, the string collection is empty but when I submit, the field says valid (border green)

UPDATE: After some debugging, if I initialize with

IEnumerable<string> multipleLocations;

instead of

IEnumerable<string> multipleLocations = new string[] { };

The validation will trigger correctly if none is selected. If you make the component dirty by selecting one item and then deselect, the validation won't trigger. What I see here is to force the variable being null on Change event.

Cheers