问题描述
我正在尝试从输入库派生Blazor上的editform定制输入,但是由于最近才刚接触本周Blazor和本月的C#,因此我一直在努力掌握它。
我发现了 https://www.meziantou.net/creating-a-inputselect-component-for-enumerations-in-blazor.htm(或在下面找到粘贴的代码) 并能够将其用于inputselect内的可为空的枚举,但是尝试将其复制为可为空的输入复选框则无济于事。我想知道是否有人链接或会知道如何对其进行调整以使其正常工作。
提前谢谢您,我几乎整天都在我的电脑上,所以请随时提出问题,不要not惜我哈哈。
// file: Shared/InputSelectEnum.cs
using System;
using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Reflection;
using Humanizer;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Forms;
using Microsoft.AspNetCore.Components.Rendering;
// Inherit from InputBase so the hard work is already implemented ?
// Note that adding a constraint on TEnum (where T : Enum) doesn't work when used in the view,Razor raises an error at build time. Also,this would prevent using nullable types...
namespace OrderServiceFrontEnd.Shared
{
public sealed class InputSelectEnum<TEnum> : InputBase<TEnum>
{
// Generate html when the component is rendered.
protected override void buildrenderTree(RenderTreeBuilder builder)
{
builder.OpenElement(0,"select");
builder.AddMultipleAttributes(1,AdditionalAttributes);
builder.AddAttribute(2,"class",CssClass);
builder.AddAttribute(3,"value",BindConverter.FormatValue(CurrentValueAsstring));
builder.AddAttribute(4,"onchange",EventCallback.Factory.CreateBinder<string>(this,value => CurrentValueAsstring = value,CurrentValueAsstring,null));
// Add an option element per enum value
var enumType = GetEnumType();
foreach (TEnum value in Enum.GetValues(enumType))
{
builder.OpenElement(5,"option");
builder.AddAttribute(6,value.ToString());
builder.AddContent(7,GetdisplayName(value));
builder.CloseElement();
}
builder.CloseElement(); // close the select element
}
protected override bool TryParseValueFromString(string value,out TEnum result,out string validationErrorMessage)
{
// Let's Blazor convert the value for us ?
if (BindConverter.TryConvertTo(value,CultureInfo.CurrentCulture,out TEnum parsedValue))
{
result = parsedValue;
validationErrorMessage = null;
return true;
}
// Map null/empty value to null if the bound object is nullable
if (string.IsNullOrEmpty(value))
{
var nullableType = Nullable.GetUnderlyingType(typeof(TEnum));
if (nullableType != null)
{
result = default;
validationErrorMessage = null;
return true;
}
}
// The value is invalid => set the error message
result = default;
validationErrorMessage = $"The {FieldIdentifier.FieldName} field is not valid.";
return false;
}
// Get the display text for an enum value:
// - Use the displayAttribute if set on the enum member,so this support localization
// - Fallback on Humanizer to decamelize the enum member name
private string GetdisplayName(TEnum value)
{
// Read the display attribute name
var member = value.GetType().GetMember(value.ToString())[0];
var displayAttribute = member.GetCustomAttribute<displayAttribute>();
if (displayAttribute != null)
return displayAttribute.GetName();
// Require the NuGet package Humanizer.Core
// <packagereference Include = "Humanizer.Core" Version = "2.8.26" />
return value.ToString().Humanize();
}
// Get the actual enum type. It unwrap Nullable<T> if needed
// MyEnum => MyEnum
// MyEnum? => MyEnum
private Type GetEnumType()
{
var nullableType = Nullable.GetUnderlyingType(typeof(TEnum));
if (nullableType != null)
return nullableType;
return typeof(TEnum);
}
}
}
Blazor comp:
<InputSelectEnum @bind-Value="@_Order.IOSAppDetails.PhasedRelease"/>
解决方法
作为[x]标签的替代方法,将该值设置为null
:
如果您希望在true,false,null
之间循环,则可以强制OnChangeAction
将值设置为null
(如果以前是false
)。
利用控件上的hidden
属性来隐藏和显示<input>
和<label>
@inherits InputBase<bool?>
<input type="checkbox" value="@CurrentValue" @attributes="AdditionalAttributes" class="@CssClass" style="width:15px; height:15px;vertical-align:-2px;"
@onchange="EventCallback.Factory.CreateBinder<bool?>(this,OnChangeAction,this.CurrentValueAsBool)" hidden="@_HideCheckBox" />
<label @onclick="SetValueToTrue" hidden="@(!_HideCheckBox)" style="width:15px;height:15px;margin-left:-5px;">[?]</label>
@code {
bool _HideCheckBox { get; set; } = false;
bool? _CurrentValueAsBool;
private bool? CurrentValueAsBool
{
get
{
if (string.IsNullOrEmpty(CurrentValueAsString))
_CurrentValueAsBool = null;
else
{
if (bool.TryParse(CurrentValueAsString,out bool _currentBool))
_CurrentValueAsBool = _currentBool;
else
_CurrentValueAsBool = null;
}
SetCheckBoxCheckedAttribute(_CurrentValueAsBool);
return _CurrentValueAsBool;
}
set => _CurrentValueAsBool = value;
}
void SetCheckBoxCheckedAttribute(bool? _currentValueAsBool)
{
bool _isChecked = _currentValueAsBool.HasValue ? _currentValueAsBool.Value : false;
var _checkBoxAttributes = AdditionalAttributes != null ? AdditionalAttributes.ToDictionary(kv => kv.Key,kv => kv.Value) : new Dictionary<string,object>(); ;
if (!_isChecked)
{
_ = _checkBoxAttributes.ContainsKey("checked") ? _checkBoxAttributes["checked"] = false : _checkBoxAttributes.TryAdd("checked",false);
if (!_currentValueAsBool.HasValue)
_HideCheckBox = true;
}
else
{
_HideCheckBox = false;
_ = _checkBoxAttributes.ContainsKey("checked") ? _checkBoxAttributes["checked"] = true : _checkBoxAttributes.TryAdd("checked",true);
}
AdditionalAttributes = _checkBoxAttributes;
}
protected override bool TryParseValueFromString(string value,out bool? result,out string validationErrorMessage)
{
validationErrorMessage = null;
if (string.IsNullOrEmpty(value))
{
result = null;
}
else
{
if (bool.TryParse(value,out bool _result))
{
result = _result;
}
else
{
validationErrorMessage = "Unable to parse value!";
result = null;
return false;
}
}
return true;
}
private Action<Nullable<bool>> OnChangeAction
{
get => (_inputValue) =>
{
//ignore input value if previously false,to force it to null
if (this.CurrentValueAsString == bool.FalseString)
{
_inputValue = null;
this.CurrentValueAsString = string.Empty;
}
else
this.CurrentValueAsString = _inputValue.HasValue ? _inputValue.Value.ToString() : string.Empty;
};
}
void SetValueToTrue(MouseEventArgs e)
{
this.CurrentValueAsString = bool.TrueString;
}
}
您可以将<label>
更改为<image>
或使用字体图标使其美观。
组件的使用保持不变。
@*.other fields.*@
<label>Nullable value:</label><NullableBoolCheckBox @bind-Value="someModel.SomeNullBoolValue" />
<br />
<strong>value is: @(someModel.SomeNullBoolValue.HasValue?$"{someModel.SomeNullBoolValue}":"null")</strong>
<br />
@*.other fields.*@
,
您可以继承InputBase<bool?>
类并使用一些其他属性处理绑定值。
在此示例中,尽管看起来或多或少相同,但我没有使用“代码隐藏”方法。
该组件位于名为NullableBoolCheckBox.razor
的文件中
@inherits InputBase<bool?>
<input type="checkbox" value="@CurrentValue" @attributes="AdditionalAttributes" class="@CssClass" style="width:15px; height:15px;vertical-align:-2px;"
@onchange="EventCallback.Factory.CreateBinder<bool?>(this,this.CurrentValueAsBool)" />
<label @onclick="SetValueToNull" style="width:15px;height:15px;">[x]</label>
@code {
bool? _CurrentValueAsBool;
private bool? CurrentValueAsBool
{
get
{
if (string.IsNullOrEmpty(CurrentValueAsString))
_CurrentValueAsBool = null;
else
{
if (bool.TryParse(CurrentValueAsString,out bool _currentBool))
_CurrentValueAsBool = _currentBool;
else
_CurrentValueAsBool = null;
}
SetCheckBoxCheckedAttribute(_CurrentValueAsBool);
return _CurrentValueAsBool;
}
set => _CurrentValueAsBool = value;
}
void SetCheckBoxCheckedAttribute(bool? _currentValueAsBool)
{
bool _isChecked = _currentValueAsBool.HasValue ? _currentValueAsBool.Value : false;
var _attributes = AdditionalAttributes != null ? AdditionalAttributes.ToDictionary(kv => kv.Key,object>(); ;
if (!_isChecked)
{
_ = _attributes.ContainsKey("checked") ? _attributes["checked"] = false : _attributes.TryAdd("checked",false);
}
else
{
_ = _attributes.ContainsKey("checked") ? _attributes["checked"] = true : _attributes.TryAdd("checked",true);
}
AdditionalAttributes = _attributes;
}
protected override bool TryParseValueFromString(string value,out bool _result))
{
result = _result;
}
else
{
validationErrorMessage = "Unable to parse value!";
result = null;
return false;
}
}
return true;
}
private Action<Nullable<bool>> OnChangeAction { get => (_inputValue) => CurrentValueAsString = _inputValue.HasValue ? _inputValue.Value.ToString() : null; }
void SetValueToNull(MouseEventArgs e)
{
this.CurrentValueAsString = string.Empty;
}
}
它可以与任何其他组件相同的方式使用。
例如:
<EditForm Model="someModel">
@*.more fields.*@
<label>Nullable value:</label><NullableBoolCheckBox @bind-Value="someModel.SomeNullBoolValue" />
<br />
<strong>value is: @(someModel.SomeNullBoolValue.HasValue?$"{someModel.SomeNullBoolValue}":"null")</strong>
@*.more fields.*@
</EditForm>
链接到表单的模型具有属性:public bool? SomeNullBoolValue { get; set; }
,该属性绑定到复选框。
如果您不想使用[x]标签重设值,则可以执行诸如点击计数之类的操作来循环遍历值true,null
。