Unhandled exception rendering component: '<' is an invalid start of a value

2022-02-22 乐帮网

netcore

我的项目（.Net6）编译后运行报错如下：

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.JsonConverter`1[[dts.master.pro.Client.ViewModel.Index.DbModel, dts.master.pro.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].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.JsonConverter`1[[dts.master.pro.Client.ViewModel.Index.DbModel, dts.master.pro.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.JsonSerializer.ReadCore[DbModel](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.JsonSerializer.ReadCore[DbModel](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
at System.Text.Json.JsonSerializer.ContinueDeserialize[DbModel](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonConverter converter, JsonSerializerOptions options)
at System.Text.Json.JsonSerializer.<ReadAllAsync>d__65`1[[dts.master.pro.Client.ViewModel.Index.DbModel, dts.master.pro.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
at System.Net.Http.Json.HttpContentJsonExtensions.<ReadFromJsonAsyncCore>d__4`1[[dts.master.pro.Client.ViewModel.Index.DbModel, dts.master.pro.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
at System.Net.Http.Json.HttpClientJsonExtensions.<GetFromJsonAsyncCore>d__13`1[[dts.master.pro.Client.ViewModel.Index.DbModel, dts.master.pro.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
at dts.master.pro.Client.Pages.Index.OnInitializedAsync() in E:\code\git\hy\dts\HVDTS\dts.master\Client\Pages\Index.razor.cs:line 39
at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

这个错误的原因也很简单，就是调用方法的时候（API）返回的结果和预期的一致引起来的。比如我在后台有一段这样的代码：

 var data = await _http.GetFromJsonAsync<Model>("/regs/index");

但是这个/regs/index接口返回中的并不是json格式的字符串，或者是报错了就直接返回一个500错误的页面。这时就会引发上面的错误，所以还是从解决接口错误开始找起。

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