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First of all, i am in process of learning Blazor. I keep getting 'unhandled error occured' when Create component should load. The problem is when i add <inputselect> to EditForm and @bind-Value to one of model's property and try to populate list with values from database.

What I have tried:

Create component:
Razor
<pre>@page "/products/create"
@inject HttpClient client
@inject NavigationManager uriHelper

<h1>Create new product</h1>
<hr />

<EditForm Model="@model" OnValidSubmit="@validSubmit">
    <DataAnnotationsValidator/>
    <div class="form-group">
        <label>Code :</label>
        <div>
            <InputText @bind-Value="@model.Code"/>
            <ValidationMessage For="@(()=>model.Code)"/>
        </div>
    </div>
    <div class="form-group">
        <label>Name :</label>
        <div>
            <InputText @bind-Value="@model.Name" />
            <ValidationMessage For="@(()=>model.Name)" />
        </div>
    </div>
    <div class="form-group">
        <label>Category :</label>
        <div>
            
            <InputSelect @bind-Value="@model.Category">
                @foreach (var item in categories)
                {
                    <option>@item</option>
                }
            </InputSelect>
            <ValidationMessage For="@(()=>model.Category)" />
        </div>
    </div>
</EditForm>

@code{
    ProductsViewModel model = new ProductsViewModel();

    string[] categories { get; set; }

    protected override async Task OnInitializedAsync()
    {
        categories = await client.GetFromJsonAsync<string[]>("api/products/categories");
    }

    async Task validSubmit()
    {
        await client.PostAsJsonAsync("api/products", model);
        uriHelper.NavigateTo("products");
    }
}

ProductsController:

C#
[Route("categories")]
        [HttpGet]
        public string[] GetCategories()
        {
            return categoriesService.GetAllAsync().Result.Select(e => e.Name).ToArray();
        }

It populates categories array but it does not show Create component with populated list.
Posted
Updated 2-Mar-22 8:12am

1 solution

You need to look at the Blazor Component Lifecycle to understand why you have this problem. ref: ASP.NET Core Razor component lifecycle | Microsoft Docs[^]

Have a read of this section of the information: Handle incomplete async actions at render[^]

I recommend Blazor University – Learn the new .NET SPA framework from Microsoft[^] as a good learning resource.
   

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