Internal Null Reference Exception in DropDown Component

Question

Hello,The scenario involves the initialization of an edit form. There are two instances of a custom dropdown component that wrap a SyncfusionDropDown component. On the form. They load there data asynchronously from a server endpoint. Both components have their Value prop set to fields on the model. When the form loads the following null reference exception is thrown:blazor.webassembly.js:1 crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100] Unhandled exception rendering component: Object reference not set to an instance of an object.System.NullReferenceException: Object reference not set to an instance of an object. at Syncfusion.Blazor.DropDowns.SfDropDownList`2.d__597[[System.Nullable`1[[System.Int32, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[SyncfusionIssueSample.Client.Pages.Index.DropDownOption, SyncfusionIssueSample.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext() at Syncfusion.Blazor.DropDowns.SfDropDownList`2.d__596[[System.Nullable`1[[System.Int32, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[SyncfusionIssueSample.Client.Pages.Index.DropDownOption, SyncfusionIssueSample.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext() at Syncfusion.Blazor.DropDowns.SfDropDownList`2.d__534[[System.Nullable`1[[System.Int32, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[SyncfusionIssueSample.Client.Pages.Index.DropDownOption, SyncfusionIssueSample.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext() at Syncfusion.Blazor.DropDowns.SfDropDownList`2.d__528[[System.Nullable`1[[System.Int32, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[SyncfusionIssueSample.Client.Pages.Index.DropDownOption, SyncfusionIssueSample.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext() at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)Here is the minimal reproduction of the issue:Form code:@page "/"@using Syncfusion.Blazor.Inputs;@using SyncfusionIssueSample.Client.Shared@using SyncfusionIssueSample.Shared;@if (editContext != null){ }@code { public ModelClass? model; public EditContext editContext; protected override async Task OnInitializedAsync() { model = new ModelClass(); model.FieldOne = 1; model.FieldTwo = 1; editContext = new EditContext(model); } public class DropDownOption { public int? Value { get; set; } public string DisplayText { get; set; } } public class ModelClass { public int? FieldOne { get; set; } public int? FieldTwo { get; set; } }}Custom component code:@using Syncfusion.Blazor.Inputs;@using SyncfusionIssueSample.Shared;@using static SyncfusionIssueSample.Client.Pages.Index; @code { [Parameter] public EventCallback ValueChanged { get; set; } [Parameter] public int? Value { get; set; } private SfDropDownList DropDownList; private List options = new List(); private bool dataLoaded = false; protected override async Task OnParametersSetAsync() { if (!dataLoaded) { dataLoaded = true; var result = (await GetDropDownOptions()).ToList(); options = result; } } private async Task OnValueChange(ChangeEventArgs args) { await ValueChanged.InvokeAsync(args.Value); } public async Task> GetDropDownOptions() { List options = new List(); options.Add(new DropDownOption() { Value = 1, DisplayText = "Option 1" }); options.Add(new DropDownOption() { Value = 2, DisplayText = "Option 2" }); options.Add(new DropDownOption() { Value = 3, DisplayText = "Option 3" }); await Task.Delay(1000); return options; }}The issue seems to involve a combination of the asynchronous data load of the dropdown data, the presence of the change event handlers, and the existence of two or more dropdowns on the form whose field is bound to the form model. It would appear that a value change event is firing, which is causing a state change within the form, and a subsequent on OnParametersSetAsync() call to the other dropdown. However, I don't know how to resolve the issue since it's originating from within the Syncfusion dropdown.Any guidance here would be much appreciated. I've attached a minimal sandbox reproduction of the issue. Thank you.Attachment: SyncfusionIssueSample_1a80584c.zip

Kokila Poovendran · Answer

Hi Enoch,Greeting from Syncfusion support!We apologize for the inconvenience caused by the issue. We appreciate your effort in sharing the code snippet as well as a runnable sample to reproduce the issue.We have investigated the issue with the latest package version 23.1.43, and we can confirm that it resolves the problem. The issue you mentioned does not occur in the latest version. To resolve this issue on your end, we recommend upgrading the package to version "23.1.43."Thank you for your understanding and for bringing this to our attention.Regards,Kokila Poovendran.

Enoch · Answer

Hi Kokila,This resolved my issue and some others as well related to the dropdown. Thank you for your response!

Shereen Shajahan · Answer

Hi Enoch,Glad to know your issue has been resolved. Please get back to us for assistance in the future.Regards,Shereen

Muhammad WaqasAziz · Answer

I have the exact same issueDotnet 8.0Syncfusion Blazor version 23.1.44Cent per Cent Exact behaviour

Kokila Poovendran · Answer

Hi Enoch,We apologize for the inconvenience caused by the issue. We have investigated the issue with the latest package version 24.2.4, and we can confirm that it resolves the problem. The issue you mentioned does not occur in the latest version. To resolve this issue on your end, we recommend upgrading the package to version "24.2.4."Regards,Kokila Poovendran.

Stephen · Answer

I am having the same issue with v25.1.41 - Please has this been resolved in version 25? If so, which? See error below.

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]

Unhandled exception rendering component: Object reference not set to an instance of an object.

System.NullReferenceException: Object reference not set to an instance of an object.

at ProjectMarks.Frontend.Client.Pages.Project.PActions.<BuildRenderTree>b__0_12(RenderTreeBuilder __builder3)

at Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddContent(Int32 sequence, RenderFragment fragment)

at Syncfusion.Blazor.Grids.GridColumns.<BuildRenderTree>b__23_0(RenderTreeBuilder __builder2)

at Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddContent(Int32 sequence, RenderFragment fragment)

at Microsoft.AspNetCore.Components.CascadingValue`1[[Syncfusion.Blazor.Grids.GridColumns, Syncfusion.Blazor.Grids, Version=25.1.41.0, Culture=neutral, PublicKeyToken=3d67ed1f87d44c89]].Render(RenderTreeBuilder builder)

at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)