Multiselect listbox does not return ienum

Radzen Studio Blazor Server
1

The same issue as described here: ListBox Save
When using a ListBox with multiselect, the return is only a single object which results in an enumeration error:

I have reproduced this with the demo project on the latest version.

Unhandled exception rendering component: Collection was modified; enumeration operation may not execute.System.InvalidOperationException: Collection was modified; enumeration operation may not execute.

2

The ListBox with multiple selection in our demo is working normally:
https://blazor.radzen.com/listbox

You can check the code for reference:

<RadzenListBox @bind-Value="multipleValues" ... />
...
IEnumerable<string> multipleValues = new string[] { "ALFKI", "ANATR" };
...
3

Thank you for your reply, @enchev
That is the exact code I'm using, and unfortunately I still get the same error, and only with multiple value selections.

My intention is to use a list of strings as options, and retrieve the selections back. Unfortunately I'm unable to get the example to work, yet the normal radzen checkbox code is working fine for me.

Can you think of anything else I can do to troubleshoot this error, or have any examples of the proper usage without entityframework?

4

Hello,

Sorry if i bring up a somewhat old conversation.
I would just like to say that i have the same problem as @Joseph_Namey.
i have tried to mirror the code in the documentation but i still get the error:

    blazor.server.js:15 [2020-04-27T18:00:45.478Z] Error: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
       at System.Collections.Generic.List`1.Enumerator.MoveNext()
       at System.Linq.Enumerable.CastIterator[TResult](IEnumerable source)+MoveNext()
       at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
       at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)
       at Radzen.DropDownBase`1.SelectItemFromValue(Object value)
       at Radzen.DropDownBase`1.OnParametersSetAsync()
       at Microsoft.AspNetCore.Components.ComponentBase.CallOnParametersSetAsync()
       at Microsoft.AspNetCore.Components.ComponentBase.SetParametersAsync(ParameterView parameters)
       at Radzen.DataBoundFormComponent`1.SetParametersAsync(ParameterView parameters)
       at Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.UpdateRetainedChildComponent(DiffContext& diffContext, Int32 oldComponentIndex, Int32 newComponentIndex)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForFramesWithSameSequence(DiffContext& diffContext, Int32 oldFrameIndex, Int32 newFrameIndex)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(DiffContext& diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForFramesWithSameSequence(DiffContext& diffContext, Int32 oldFrameIndex, Int32 newFrameIndex)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(DiffContext& diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForFramesWithSameSequence(DiffContext& diffContext, Int32 oldFrameIndex, Int32 newFrameIndex)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(DiffContext& diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForFramesWithSameSequence(DiffContext& diffContext, Int32 oldFrameIndex, Int32 newFrameIndex)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(DiffContext& diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl)
       at Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.ComputeDiff(Renderer renderer, RenderBatchBuilder batchBuilder, Int32 componentId, ArrayRange`1 oldTree, ArrayRange`1 newTree)
       at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment)
       at Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderInExistingBatch(RenderQueueEntry renderQueueEntry)
       at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()

Can anyone please help me out? This error happens as soon that i try to click one of the options i have defined.

5

Hi @Darkis, @Joseph_Namey,

It's really important you convert your query to list in order to avoid this error.
I mean, query you are binding to Data parameter in RadzenListBox.

6

Congratulations on nice control suite.

I am also facing this issue.

My environment is .net 5.0

Strange thing is it works and then crashes after x number of selected items.

Any thoughts would be appreciated.

7

Managed to "resolve". Thanks!