从json中获取项目，并将其作为参数传递给Blazor wasm

Question

嗨，我有一个问题，我的对象在Blazor web组装。我有我的组件ShipmentsTable，我将装运作为参数传递，但是有一个问题，因为我的GetShipmentResult看起来像这样[![1]][1]

<ShipmentsTable Shipments="@shipments.Items"></ShipmentsTable>
@code {
private GetShipmentsResult shipments;
protected override async Task OnInitializedAsync()
{
shipments = await HttpClient.GetFromJsonAsync<GetShipmentsResult>("https://localhost:5001/api/shipment?page=0");
}
private void NavigateToShipmentForm()
{
NavigationManager.NavigateTo("addShipment");
}

}

我的GetShipmentResult对象

public class GetShipmentsResult
{   
public List<ShipmentVm> Items { get; set; } = new List<ShipmentVm>();
public int TotalCount { get; set; }
}

和Json响应表单Api

{
"items": [
{
"description": "second",
"expectedTimeOfArrival": "2021-09-10T17:56:24.589",
"expectedTimeOfDeparture": "2021-09-10T17:56:24.589",
"actualTimeOfArrival": null,
"actualTimeOfDeparture": null,
"isDone": false,
"placeOfArrivalId": 1,
"placeOfArrival": null,
"placeOfDepartureId": 1,
"placeOfDeparture": null,
"hash": "tyac2NpISm4t/DjyGhTKnN11EKjsewr5ydNhjrzblMw=",
"index": 0,
"prevHash": "LX3OqOZpt88fvTIQfoiLs0zzoEbNBMCMdV1QsqNVRRk=",
"timeStamp": "2021-09-23T11:52:51.8174364"
}
],
"totalCount" : 1
}
public class ShipmentVm
{
public string Description { get; set; }
public DateTime ExpectedTimeOfArrival { get; set; }
public DateTime ExpectedTimeOfDeparture { get; set; }
public DateTime? ActualTimeOfArrival { get; set; }
public DateTime? ActualTimeOfDeparture { get; set; }
public bool IsDone { get; set; }
public int PlaceOfArrivalId { get; set; }
public int PlaceOfDepartureId { get; set; }
public byte[] Hash { get; set; }
public byte[] PrevHash { get; set; }
public int Index { get; set; }
public DateTime TimeStamp { get; set; }
}

blazor.webassembly.js:1 . crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]未处理的异常呈现组件:对象引用未设置为对象的实例。系统。NullReferenceException:对象引用没有设置为对象的实例。在Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.UpdateRetainedChildComponent (DiffContext&diffContext, Int32 oldComponentIndex, Int32 newComponentIndex)在Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForFramesWithSameSequence (DiffContext&diffContext, Int32 oldFrameIndex, Int32 newFrameIndex)在Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange (DiffContext&diffContext, Int32 oldStartIndex, Int32 oldEndIndexExcl, Int32 newStartIndex, Int32 newEndIndexExcl在Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder。ComputeDiff(Renderer Renderer, RenderBatchBuilder, batchBuilder, Int32 componentId, ArrayRange1 oldTree, ArrayRange1 newTree)在Microsoft.AspNetCore.Components.Rendering.ComponentState。RenderIntoBatch(RenderBatchBuilder, batchBuilder, RenderFragment)在Microsoft.AspNetCore.Components.RenderTree.Renderer。RenderInExistingBatch (RenderQueueEntry RenderQueueEntry)在Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue ()

@using TrakkerWASM.Client.Models
@using TrakkerWASM.Client.Models.TestVm
<h3>Shipments table</h3>
<table class="table table-striped">
<thead>
<tr>
<th>Is done</th>
<th>Time stamp</th>
<th>Hash</th>
<th>Previous hash</th>
</tr>
</thead>
<tbody>
@foreach (var shipment in Shipments)
{
<tr>
<td>@shipment.IsDone</td>
</tr>
<tr>
<td>@shipment.TimeStamp</td>
</tr>
<tr>
<td>@shipment.Hash.ToString()</td>
</tr>
<tr>
<td>@shipment.PrevHash</td>
</tr>
}
</tbody>
</table>
@code {
[Parameter]
public List<ShipmentVm> Shipments { get; set; }
}

Answer 1

GetFromJsonAsync有时会给出一个奇怪的结果。尝试使用Newtonsoft。Json，也许你会看到区别。我通常使用这样的算法

protected override async Task OnInitializedAsync()
{
var response = await HttpClient.GetAsync("https://localhost:5001/api/shipment?page=0");
if (response.IsSuccessStatusCode)
{
var stringData = await response.Content.ReadAsStringAsync();
shipments = JsonConvert.DeserializeObject<GetShipmentsResult>(stringData);
}

}

你还必须改变你的VM，因为反序列化器不识别字节[]

public string Hash { get; set; }
public string PrevHash { get; set; }

或者你可能需要这样的东西

[JsonProperty("hash")]
public string HashString { get; set; }
[JsonProperty("prevHash")]
public string PrevHashString { get; set; }
public byte[] Hash { 
get { return Convert.FromBase64String(HashString);} 
set { HashString=  System.Text.Encoding.UTF8.GetString(value, 0, value.Length); }
}
public byte[] PrevHash { 
get { return Convert.FromBase64String(PrevHashString);} 
set { PrevHashString=  System.Text.Encoding.UTF8.GetString(value, 0, value.Length); } 
}