在自定义select blazor组件中进行选择时回调
我在做一个Blazor Wasm。我想创建自己的自定义在自定义select blazor组件中进行选择时回调,blazor,blazor-client-side,Blazor,Blazor Client Side,我在做一个Blazor Wasm。我想创建自己的自定义选择组件。下面的实现可以工作,但缺少一些东西:当在自定义选择组件中选择某个内容时,没有回调。我希望能够从TestView.razor组件捕获事件 我的自定义实现InputSelectCustom.cs public class InputSelectCustom<T> : InputSelect<T> { protected override string FormatValueAsString(T value
选择组件。下面的实现可以工作,但缺少一些东西:当在自定义选择组件中选择某个内容时,没有回调。我希望能够从TestView.razor组件捕获事件
我的自定义实现InputSelectCustom.cs
public class InputSelectCustom<T> : InputSelect<T>
{
protected override string FormatValueAsString(T value)
{
// Custom code ommitted for clarity
return base.FormatValueAsString(value);
}
protected override bool TryParseValueFromString(string value, out T result, out string validationErrorMessage)
{
if (typeof(T) == typeof(int) ||
typeof(T) == typeof(int?))
{
if (int.TryParse(value, out var resultInt))
{
result = (T)(object)resultInt;
validationErrorMessage = null;
return true;
}
else
{
result = default;
validationErrorMessage = "The chosen value is not valid.";
return false;
}
}
else
if (typeof(T).IsEnum)
{
if (CustomFunctions.EnumTryParse<T>(value, out var resultEnum))
{
result = (T)(object)resultEnum;
validationErrorMessage = null;
return true;
}
else
{
result = default;
validationErrorMessage = "The chosen value is not valid.";
return false;
}
}
else
if (typeof(T).IsNullableEnum())
{
if (CustomFunctions.NullableEnumTryParse<T>(value, out var resultEnum))
{
result = (T)(object)resultEnum;
validationErrorMessage = null;
return true;
}
else
{
result = default;
validationErrorMessage = "The chosen value is not valid.";
return false;
}
}
else
{
return base.TryParseValueFromString(value, out result, out validationErrorMessage);
}
}
protected override Task OnParametersSetAsync()
{
return base.OnParametersSetAsync();
}
}
更新
所以我需要的是一种在我选择的值发生变化时得到通知的方式
起初,我试着这样做:
<InputSelectCustom @bind-Value="CurrentFilterModel.ClassmentFilter">
<option value=""> Show all content </option>
<option value="@EnumClassment.Popular"> Popular </option>
<option value="@EnumClassment.Featured"> Featured </option>
<option value="@EnumClassment.Novelty"> Novelty </option>
</InputSelectCustom>
这一次,一切都按预期进行:每当用户选择另一个值时,我都会收到新值的通知,我可以立即执行自定义代码
如果我错了,请纠正我,或者这可以用一种更优雅的方式来完成,因为我对Blazor是新手,也许我错过了什么
PS:使用字符串、整数和枚举进行测试。你不能这样做,也不应该这样做。为何
但是,您可以像使用单选按钮那样执行此操作,但是您的自定义组件应该派生自InputBase,并提供Razor标记和逻辑
在自定义选择组件中选择某个内容时,没有回调
当然会有回电。。。否则,如何使用新值更新模型。它由InputBase组件的CurrentValue属性触发:
protected TValue CurrentValue
{
get => Value;
set
{
var hasChanged = !EqualityComparer<TValue>.Default.Equals(value,
Value);
if (hasChanged)
{
Value = value;
_ = ValueChanged.InvokeAsync(value);
EditContext.NotifyFieldChanged(FieldIdentifier);
}
}
}
以下是自定义选择组件的代码。请注意,InputSelect不支持int等数值类型(您不能将其应用于int属性,例如公共int Country{get;set;}
),或者(不确定,需要检查…)。枚举类型也不支持。我的组件支持这样的值:
InputSelectNumber.cs
希望这有助于…感谢您对我的问题感兴趣。请查看我更新的问题。您关于将事件处理程序实现到onfildChanged
的建议在我的案例中非常完美。很高兴了解这一点。再次感谢。我使我的组件IDisposable
并添加了Dispose方法(因为事件处理程序)但那是另一回事。。。
<InputSelectCustom @bind-Value="CurrentFilterModel.ClassmentFilter">
<option value=""> Show all content </option>
<option value="@EnumClassment.Popular"> Popular </option>
<option value="@EnumClassment.Featured"> Featured </option>
<option value="@EnumClassment.Novelty"> Novelty </option>
</InputSelectCustom>
<InputSelectCustom @bind-Value="CurrentFilterModel.ClassmentFilter" ValueChanged="ValueChangedForClassmentFilter">
<option value=""> Show all content </option>
<option value="@EnumClassment.Popular"> Popular </option>
<option value="@EnumClassment.Featured"> Featured </option>
<option value="@EnumClassment.Novelty"> Novelty </option>
</InputSelectCustom>
<InputSelectCustom Value="@CurrentFilterModel.ClassmentFilter" ValueExpression="@( () => CurrentFilterModel.ClassmentFilter )" ValueChanged="@( (EnumClassment? s) => ValueChangedForClassmentFilter(s) )">
<option value=""> Show all content </option>
<option value="@EnumClassment.Popular"> Popular </option>
<option value="@EnumClassment.Featured"> Featured </option>
<option value="@EnumClassment.Novelty"> Novelty </option>
</InputSelectCustom>
protected async Task ValueChangedForClassmentFilter(EnumClassment? theUserInput)
{
// You have to update the model manually because handling the ValueChanged event does not let you use @bind-Value
// For the validation to work you must now also define the ValueExpression because @bind-Value did it for you
CurrentFilterModel.ClassmentFilter = theUserInput;
// Refresh data based on filters
await FilterCoursesServerSide();
}
protected TValue CurrentValue
{
get => Value;
set
{
var hasChanged = !EqualityComparer<TValue>.Default.Equals(value,
Value);
if (hasChanged)
{
Value = value;
_ = ValueChanged.InvokeAsync(value);
EditContext.NotifyFieldChanged(FieldIdentifier);
}
}
}
_ = ValueChanged.InvokeAsync(value);
public class InputSelectNumber<T> : InputSelect<T>
{
protected override bool TryParseValueFromString(string value, out T
result, out string validationErrorMessage)
{
if (typeof(T) == typeof(int))
{
if (int.TryParse(value, out var resultInt))
{
result = (T)(object)resultInt;
validationErrorMessage = null;
return true;
}
else
{
result = default;
validationErrorMessage = "The chosen value is not a valid
number.";
return false;
}
}
else
{
return base.TryParseValueFromString(value, out result, out
validationErrorMessage);
}
}
}
<EditForm EditContext="@EditContext">
<DataAnnotationsValidator />
<div class="form-group">
<label for="name">Enter your Name: </label>
<InputText Id="name" Class="form-control" @bind-Value="@comment.Name">
</InputText>
<ValidationMessage For="@(() => comment.Name)" />
</div>
<div class="form-group">
<label for="body">Select your country: </label>
<InputSelectNumber @bind-Value="@comment.Country">
<option value="">Select country...</option>
<option value="1">USA</option>
<option value="2">Britain</option>
<option value="3">Germany</option>
<option value="4">Israel</option>
</InputSelectNumber>
<label for="body">Select your country: </label>
<ValidationMessage For="@(() => comment.Country)" />
</div>
<p>
<button type="submit">Submit</button>
</p>
</EditForm>
<p>Name: @comment.Name</p>
<p>Country: @comment.Country</p>
@code
{
private EditContext EditContext;
private Comment comment = new Comment();
protected override void OnInitialized()
{
EditContext = new EditContext(comment);
}
public class Comment
{
public string Name { get; set; }
// Note that with the subclassed InputSelectNumber I can use either string
// or int. In both cases no error occurs.
public string Country { get; set; }
//public int Country { get; set; }
}
}
private EditContext EditContext;
private Comment Model = new Comment();
protected override void OnInitialized()
{
EditContext = new EditContext(Model);
EditContext.OnFieldChanged += EditContext_OnFieldChanged;
base.OnInitialized();
}
// Note: The OnFieldChanged event is raised for each field in the
model
private void EditContext_OnFieldChanged(object sender,
FieldChangedEventArgs e)
{
Console.WriteLine(e.FieldIdentifier.FieldName);
// more code...
}