just started with Blazor created my first app its a CRUD app with api. But i get this huge error and i can't figure out what is wrong and what it actual means? think something with the api links? I've tried the Unhandled exception rendering component: '<' is an invalid start of a value for Blazor WASM solutions but none of these seems to work for me. I'm using the blazor webassembly in visualstudio 17.2.0 with entityframework.
When i start my project i get this message at the bottom of my page :
An unhandled error has occurred. Reload
blazor.webassembly.js:1 crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100] Unhandled exception rendering component: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0. System.Text.Json.JsonException: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0. ---> System.Text.Json.JsonReaderException: '<' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0. at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan
1 bytes) at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker) at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first) at System.Text.Json.Utf8JsonReader.ReadSingleSegment() at System.Text.Json.Utf8JsonReader.Read() at System.Text.Json.Serialization.JsonConverter1[[System.Collections.Generic.List1[[TreviData.Shared.Models.Ewons, TreviData.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state) --- End of inner exception stack trace --- at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex) at System.Text.Json.Serialization.JsonConverter1[[System.Collections.Generic.List1[[TreviData.Shared.Models.Ewons, TreviData.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state) at System.Text.Json.JsonSerializer.ReadCore[List1](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state) at System.Text.Json.JsonSerializer.ReadCore[List1](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase) at System.Text.Json.JsonSerializer.ContinueDeserialize[List1](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonConverter converter, JsonSerializerOptions options) at System.Text.Json.JsonSerializer.<ReadAllAsync>d__651[[System.Collections.Generic.List1[[TreviData.Shared.Models.Ewons, TreviData.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].MoveNext() at System.Net.Http.Json.HttpContentJsonExtensions.<ReadFromJsonAsyncCore>d__41[[System.Collections.Generic.List1[[TreviData.Shared.Models.Ewons, TreviData.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].MoveNext() at System.Net.Http.Json.HttpClientJsonExtensions.<GetFromJsonAsyncCore>d__131[[System.Collections.Generic.List`1[[TreviData.Shared.Models.Ewons, TreviData.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].MoveNext() at TreviData.Client.Pages.EwonDetails.GetUser() in C:\Users\toonw\source\repos\TreviData\TreviData\Client\Pages\EwonDetails.razor:line 73 at TreviData.Client.Pages.EwonDetails.OnInitializedAsync() in C:\Users\toonw\source\repos\TreviData\TreviData\Client\Pages\EwonDetails.razor:line 69 at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync() at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState) window.Module.s.printErr @ blazor.webassembly.js:1 Fe._internal.dotNetCriticalError @ blazor.webassembly.js:1 St @ blazor.webassembly.js:1 _mono_wasm_invoke_js_blazor @ dotnet.6.0.5.wc6fu8n2ms.js:1 $func219 @ 00971e46:0x1a490 $func167 @ 00971e46:0xce5e $func166 @ 00971e46:0xbd71 $func2812 @ 00971e46:0xabf01 $func1616 @ 00971e46:0x6fcc2 $func1620 @ 00971e46:0x7032f $mono_wasm_invoke_method @ 00971e46:0x969d Module._mono_wasm_invoke_method @ dotnet.6.0.5.wc6fu8n2ms.js:1 managed_BINDINGS_SetTaskSourceResult @ managed_BINDINGS_SetTaskSourceResult:17 (anonymous) @ dotnet.6.0.5.wc6fu8n2ms.js:1 Promise.then (async) _wrap_js_thenable_as_task @ dotnet.6.0.5.wc6fu8n2ms.js:1 _js_to_mono_obj @ dotnet.6.0.5.wc6fu8n2ms.js:1 _mono_wasm_invoke_js_with_args @ dotnet.6.0.5.wc6fu8n2ms.js:1 $func219 @ 00971e46:0x1a449 $func167 @ 00971e46:0xce5e $func166 @ 00971e46:0xbd71 $func2812 @ 00971e46:0xabf01 $func1616 @ 00971e46:0x6fcc2 $func1620 @ 00971e46:0x7032f $mono_wasm_invoke_method @ 00971e46:0x969d Module._mono_wasm_invoke_method @ dotnet.6.0.5.wc6fu8n2ms.js:1 managed_BINDINGS_SetTaskSourceResult @ managed_BINDINGS_SetTaskSourceResult:17 (anonymous) @ dotnet.6.0.5.wc6fu8n2ms.js:1 Promise.then (async) _wrap_js_thenable_as_task @ dotnet.6.0.5.wc6fu8n2ms.js:1 _js_to_mono_obj @ dotnet.6.0.5.wc6fu8n2ms.js:1 _mono_wasm_invoke_js_with_args @ dotnet.6.0.5.wc6fu8n2ms.js:1 $func219 @ 00971e46:0x1a449 $func167 @ 00971e46:0xce5e $func166 @ 00971e46:0xbd71 $func2812 @ 00971e46:0xabf01 $func1616 @ 00971e46:0x6fcc2 $func1614 @ 00971e46:0x6fc34 $func967 @ 00971e46:0x50685 $func219 @ 00971e46:0x1a449 $func167 @ 00971e46:0xce5e $func166 @ 00971e46:0xbd71 $func2812 @ 00971e46:0xabf01 $func1616 @ 00971e46:0x6fcc2 $func1620 @ 00971e46:0x7032f $mono_wasm_invoke_method @ 00971e46:0x969d Module._mono_wasm_invoke_method @ dotnet.6.0.5.wc6fu8n2ms.js:1 managed__Microsoft_AspNetCore_Components_WebAssembly__Microsoft_AspNetCore_Components_WebAssembly_Services_DefaultWebAssemblyJSRuntime_BeginInvokeDotNet @ managed__Microsoft_AspNetCore_Components_WebAssembly__Microsoft_AspNetCore_Components_WebAssembly_Services_DefaultWebAssemblyJSRuntime_BeginInvokeDotNet:19 beginInvokeDotNetFromJS @ blazor.webassembly.js:1 b @ blazor.webassembly.js:1 e.invokeMethodAsync @ blazor.webassembly.js:1 (anonymous) @ blazor.webassembly.js:1 ve @ blazor.webassembly.js:1 we @ blazor.webassembly.js:1 (anonymous) @ blazor.webassembly.js:1 (anonymous) @ blazor.webassembly.js:1 onGlobalEvent @ blazor.webassembly.js:1
Here is my code.
AddEwon.Razor
@page "/ewon/add/"
@page "/ewon/edit/{Id:int}"
@using TreviData.Shared.Models
@inject HttpClient Http
@inject NavigationManager NavigationManager
<h1>@Title Ewon</h1>
<hr />
<EditForm Model="@ewon" OnValidSubmit="SaveEwon">
<DataAnnotationsValidator />
<div >
<label for="Name" >EwonName</label>
<div >
<InputText @bind-Value="ewon.EwonName" />
</div>
<ValidationMessage For="@(() => ewon.EwonName)" />
</div>
<div >
<label for="Address" >ApiKey</label>
<div >
<InputText @bind-Value="ewon.ApiKey" />
</div>
<ValidationMessage For="@(() => ewon.ApiKey)" />
</div>
<div >
<button type="submit" >Save</button>
<button @onclick="Cancel">Cancel</button>
</div>
</EditForm>
@code {
[Parameter]
public int Id { get; set; }
protected string Title = "Add";
protected Ewons ewon = new();
protected override async Task OnParametersSetAsync()
{
if (Id != 0)
{
Title = "Edit";
ewon = await Http.GetFromJsonAsync<Ewons>("api/ewon/" Id);
}
}
protected async Task SaveEwon()
{
if (ewon.Id != 0)
{
await Http.PutAsJsonAsync("api/ewon", ewon);
}
else
{
await Http.PostAsJsonAsync("api/ewon", ewon);
}
Cancel();
}
public void Cancel()
{
NavigationManager.NavigateTo("/fetchewondetails");
}
}
FetchData.Razor
@page "/ewondetails"
@using TreviData.Shared.Models
@inject HttpClient Http
<h1>Ewon Data</h1>
<p>Ewons api-keys.</p>
<div >
<div >
<a href='/ewon/add' role="button">
<i ></i>
Add Ewon
</a>
</div>
<div >
<input type="text" placeholder="Search Ewon by name"
@bind="SearchString" @bind:event="oninput" @onkeyup="FilterUser" />
@if (SearchString.Length > 0)
{
<div >
<button @onclick="ResetSearch">
<i ></i>
</button>
</div>
}
</div>
</div>
<br />
@if (ewonList == null)
{
<p><em>Loading...</em></p>
}
else
{
<table >
<thead >
<tr>
<th>Id</th>
<th>Ewon Name</th>
<th>Api key</th>
</tr>
</thead>
<tbody>
@foreach (var e in ewonList)
{
<tr>
<td>@e.Id</td>
<td>@e.EwonName</td>
<td>@e.ApiKey</td>
<td>
<a href='/ewon/edit/@e.Id' role="button">
Edit
</a>
<a href='/ewon/delete/@e.Id' role="button">
Delete
</a>
</td>
</tr>
}
</tbody>
</table>
}
@code {
protected List<Ewons> ewonList = new();
protected List<Ewons> searchEwonData = new();
protected Ewons ewon = new();
protected string SearchString { get; set; } = string.Empty;
protected override async Task OnInitializedAsync()
{
await GetUser();
}
protected async Task GetUser()
{
ewonList = await Http.GetFromJsonAsync<List<Ewons>>("api/ewon");
searchEwonData = ewonList;
}
protected void FilterUser()
{
if (!string.IsNullOrEmpty(SearchString))
{
ewonList = searchEwonData
.Where(x => x.EwonName.IndexOf(SearchString, StringComparison.OrdinalIgnoreCase) != -1)
.ToList();
}
else
{
ewonList = searchEwonData;
}
}
protected void DeleteConfirm(int Id)
{
ewon = ewonList.FirstOrDefault(x => x.Id == Id);
}
public void ResetSearch()
{
SearchString = string.Empty;
ewonList = searchEwonData;
}
}
EwonController
using TreviData.Server.InterFaces;
using TreviData.Shared.Models;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
namespace TreviData.Server.Controllers
{
[Route("api/[controller]")]
[ApiController]
public class UserController : ControllerBase
{
private readonly IEwons _IEwons;
public UserController(IEwons iEwons)
{
_IEwons = iEwons;
}
[HttpGet]
public async Task<List<Ewons>> Get()
{
return await Task.FromResult(_IEwons.GetEwonDetails());
}
[HttpGet("{Id}")]
public IActionResult Get(int id)
{
Ewons ewon = _IEwons.GetEwonData(id);
if (ewon != null)
{
return Ok(ewon);
}
return NotFound();
}
[HttpPost]
public void Post(Ewons ewon)
{
_IEwons.AddEwon(ewon);
}
[HttpPut]
public void Put(Ewons ewons)
{
_IEwons.UpdateEwonDetails(ewons);
}
[HttpDelete("{Id}")]
public IActionResult Delete(int id)
{
_IEwons.DeleteEwon(id);
return Ok();
}
}
}
CodePudding user response：
I'm pretty sure the error is in the GetFromJsonAsync call returning nothing - there's a lot of code to plough through!
You are calling api/ewon/, but your controller is defined as:
[Route("api/[controller]")]
[ApiController]
public class UserController : ControllerBase
/....
which has the url "api/user".
So sort out your controller name or your calls.
You should always test your APIs with Postman!