如何使用系結值/型別引數圍繞組件制作包裝器？在mudblazormudselect

我需要圍繞mudblazor組件構建一些包裝器

所以可以說我有基本的例子：

            <MudSelect T="int" @bind-Value="@model.dict1" For="@(() => @model.dict1)" AnchorOrigin="Origin.BottomCenter">                
                    <MudSelectItem T="int"  Value="1">1</MudSelectItem>
                    <MudSelectItem T="int" Value="2">2</MudSelectItem>
            </MudSelect>

所以現在我想圍繞這個做一些包裝

<DictMudSelectComponent T="int" @bind-Value="@model.dict1" For="@(() => model.dict1)" TableName="test" AnchorOrigin="Origin.BottomCenter"></DictMudSelectComponent>

所以基于引數 TableName 我想在選擇串列中呈現不同的專案

現在我有：

DictMudSelectComponent.razor

@typeparam T
<MudSelect T="@T" @bind-Value="@Value" For="()=>For()" @attributes=AllOtherAttributes>

<MudSelectItem T="int"  Value="1">1</MudSelectItem>
<MudSelectItem T="int"  Value="2">2</MudSelectItem>
<MudSelectItem T="int"  Value="3">3</MudSelectItem>

@code {
 private Func<T> _for ;

[Parameter]
public Func<T> For
{
    get => _for;
    set
    {
        if (_for == value)
            return;
        _for = value;
    }
}

private T _value ;

[Parameter]
public T Value
{
    get => _value;
    set => _value = value;
}

[Parameter]
public string TableName { get; set; } = "";


[Parameter(CaptureUnmatchedValues = true)]
public Dictionary<string, object> AllOtherAttributes { get; set; } = new();

}

但即使這樣也行不通 - 為什么？它編譯得很好，但在渲染時我得到了

Unhandled exception rendering component: Unable to set property 'AnchorOrigin' on object of type 'MudBlazor.MudSelect`1[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]'. The error was: Specified cast is not valid.
System.InvalidOperationException: Unable to set property 'AnchorOrigin' on object of type 'MudBlazor.MudSelect`1[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]'. The error was: Specified cast is not valid.
 ---> System.InvalidCastException: Specified cast is not valid.
   at Microsoft.AspNetCore.Components.Reflection.PropertySetter.CallPropertySetter[MudSelect`1,Origin](Action`2 setter, Object target, Object value)
   at Microsoft.AspNetCore.Components.Reflection.PropertySetter.SetValue(Object target, Object value)
   at Microsoft.AspNetCore.Components.Reflection.ComponentProperties.<SetProperties>g__SetProperty|3_0(Object target, PropertySetter writer, String parameterName, Object value)
   --- End of inner exception stack trace ---
   at Microsoft.AspNetCore.Components.Reflection.ComponentProperties.<SetProperties>g__SetProperty|3_0(Object target, PropertySetter writer, String parameterName, Object value)
   at Microsoft.AspNetCore.Components.Reflection.ComponentProperties.SetProperties(ParameterView& parameters, Object target)
   at Microsoft.AspNetCore.Components.ParameterView.SetParameterProperties(Object target)
   at Microsoft.AspNetCore.Components.ComponentBase.SetParametersAsync(ParameterView parameters)
   at MudBlazor.MudBaseInput`1[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<>n__1(ParameterView parameters)
   at MudBlazor.MudBaseInput`1.<SetParametersAsync>d__177[[System.Int32, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].MoveNext()

我在這里錯過了什么？謝謝并恭祝安康

uj5u.com熱心網友回復：

好的，所以第一個問題是它需要

<MudSelect  @bind-Value="@Value"  For="@For" >

并在@code

private Expression<Func<TypeParam>>? _for;

[Parameter]
public Expression<Func<TypeParam>> For
{
    get => _for!;
    set
    {
        if (_for == value)
            return;
        _for = value;
    }
}

然后它運行沒有錯誤，但我無法更改值 - 它永遠保持在 0 /默認值 - 為什么？我現在 1/2/3 無法選擇這個硬編碼 - 總是回到 0/默認值有什么建議嗎？雷格士

編輯好的第二個問題是

 [Parameter]
 public T? Value
 {
     get => _value;
     set 
     { 
         if (!Equals(value, _value))
         {
             _value = value;
             if (ValueChanged.HasDelegate)
                 ValueChanged.InvokeAsync(_value);
         }
     }
 }

這必須檢查是否相等，因為如果不是，那么問題是 MudSelect 正在觸發引數上的 Setter，然后呼叫回呼，然后再次呼叫引數上的 Setter。

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