ASP.NET Core Blazor 属性展开和任意参数

2025-06-27

注意

此版本不是本文的最新版本。对于当前版本，请参阅本文的 .NET 9 版本。

警告

此版本的 ASP.NET Core 不再受支持。有关详细信息，请参阅 .NET 和 NET Core 支持策略。对于当前版本，请参阅本文的 .NET 9 版本。

重要

此信息与预发布产品相关，相应产品在商业发布之前可能会进行重大修改。 Microsoft 对此处提供的信息不提供任何明示或暗示的保证。

除了组件的声明参数和字段外，组件还可以捕获和呈现其他属性。其他特性可以在字典中捕获，然后在使用 @attributesRazor 指令特性呈现组件时，将其应用到称为“展开”的元素上。对于定义生成支持各种自定义项的标记元素的组件，此方案非常有用。例如，为支持多个参数或字段的元素 <input> 单独定义属性可能很繁琐。

属性展开

在下面的 Splat 组件中：

第一个 <input> 元素（id="useIndividualParams"）使用单个组件字段。
第二个 <input> 元素 (id="useAttributesDict") 使用特性展开。

Splat.razor:

@page "/splat"

<PageTitle>SPLAT!</PageTitle>

<h1>Splat Parameters Example</h1>

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

@page "/splat"

<PageTitle>SPLAT!</PageTitle>

<h1>Splat Parameters Example</h1>

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

@page "/splat"

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

@page "/splat"

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

@page "/splat"

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

@page "/splat"

<input id="useIndividualParams"
       maxlength="@maxlength"
       placeholder="@placeholder"
       required="@required"
       size="@size" />

<input id="useAttributesDict"
       @attributes="InputAttributes" />

@code {
    private string maxlength = "10";
    private string placeholder = "Input placeholder text";
    private string required = "required";
    private string size = "50";

    private Dictionary<string, object> InputAttributes { get; set; } =
        new Dictionary<string, object>()
        {
            { "maxlength", "10" },
            { "placeholder", "Input placeholder text" },
            { "required", "required" },
            { "size", "50" }
        };
}

除了id，网页中呈现的<input>元素具有相同的属性：

<input id="useIndividualParams"
       maxlength="10"
       placeholder="Input placeholder text"
       required="required"
       size="50">

<input id="useAttributesDict"
       maxlength="10"
       placeholder="Input placeholder text"
       required="required"
       size="50">

尽管前面的示例使用第一个 <input> 元素的字段（id="useIndividualParams"），但使用组件参数时，相同的行为适用。

任意属性

若要接受任意特性，请定义组件参数，并将 CaptureUnmatchedValues 属性设置为 true：

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public Dictionary<string, object>? InputAttributes { get; set; }
}

[Parameter] 上的 CaptureUnmatchedValues 属性允许参数匹配所有不匹配任何其他参数的特性。组件只能使用 CaptureUnmatchedValues 定义单个参数。与 CaptureUnmatchedValues 一起使用的属性类型必须可以使用字符串键从 Dictionary<string, object> 中分配。使用 IEnumerable<KeyValuePair<string, object>> 或 IReadOnlyDictionary<string, object> 也是此方案中的选项。

相对于元素特性位置的 @attributes 位置很重要。将 @attributes 展开到所呈现的元素上时，属性从右到左（从最后到最前）处理，对于任何共有属性，以最先被处理的属性为准。请考虑以下示例：一个父组件使用一个子组件，其中子组件设置了“extra”属性，父组件在子组件上应用了“extra”属性。

AttributeOrderChild1.razor:

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object> AdditionalAttributes { get; set; }
}

<div @attributes="AdditionalAttributes" extra="5" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object> AdditionalAttributes { get; set; }
}

AttributeOrder1.razor:

@page "/attribute-order-1"

<PageTitle>Attribute Order 1</PageTitle>

<h1>Attribute Order Example 1</h1>

<AttributeOrderChild1 extra="10" />

<p>
    View the HTML markup in your browser to inspect the attributes on
    the AttributeOrderChild1 component.
</p>

AttributeOrder1.razor:

@page "/attribute-order-1"

<PageTitle>Attribute Order 1</PageTitle>

<h1>Attribute Order Example 1</h1>

<AttributeOrderChild1 extra="10" />

<p>
    View the HTML markup in your browser to inspect the attributes on
    the AttributeOrderChild1 component.
</p>

AttributeOrderParent1.razor:

@page "/attribute-order-parent-1"

<AttributeOrderChild1 extra="10" />

AttributeOrderParent1.razor:

@page "/attribute-order-parent-1"

<AttributeOrderChild1 extra="10" />

AttributeOrderParent1.razor:

@page "/attribute-order-parent-1"

<AttributeOrderChild1 extra="10" />

AttributeOrderParent1.razor:

@page "/attribute-order-parent-1"

<AttributeOrderChild1 extra="10" />

AttributeOrderChild1 组件的 extra 属性设置为 @attributes 右侧。通过附加特性传递时，AttributeOrderParent1 组件的呈现的 <div> 包含 extra="5"，因为特性是从右到左（从最后一个到第一个）处理的。在此规则下，第一个“extra”特性会“胜出”，而这个胜出的特性正是 AttributeOrderParent1 组件中硬编码的那个 extra HTML 特性：

<div extra="5" />

在下面的示例中，子组件的<div>中extra和@attributes的顺序是颠倒的。在此场景中，通过附加特性传递时，AttributeOrderParent2 组件的呈现的 <div> 包含 extra="10"，这是因为所处理的第一个“extra”特性是从父组件展开的 extra HTML 特性。

AttributeOrderChild2.razor:

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object>? AdditionalAttributes { get; set; }
}

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object> AdditionalAttributes { get; set; }
}

<div extra="5" @attributes="AdditionalAttributes" />

@code {
    [Parameter(CaptureUnmatchedValues = true)]
    public IDictionary<string, object> AdditionalAttributes { get; set; }
}

AttributeOrder2.razor:

@page "/attribute-order-2"

<PageTitle>Attribute Order 2</PageTitle>

<h1>Attribute Order Example 2</h1>

<AttributeOrderChild2 extra="10" />

<p>
    View the HTML markup in your browser to inspect the attributes on
    the AttributeOrderChild2 component.
</p>

AttributeOrder2.razor:

@page "/attribute-order-2"

<PageTitle>Attribute Order 2</PageTitle>

<h1>Attribute Order Example 2</h1>

<AttributeOrderChild2 extra="10" />

<p>
    View the HTML markup in your browser to inspect the attributes on
    the AttributeOrderChild2 component.
</p>

AttributeOrderParent2.razor:

@page "/attribute-order-parent-2"

<AttributeOrderChild2 extra="10" />

AttributeOrderParent2.razor:

@page "/attribute-order-parent-2"

<AttributeOrderChild2 extra="10" />

AttributeOrderParent2.razor:

@page "/attribute-order-parent-2"

<AttributeOrderChild2 extra="10" />

AttributeOrderParent2.razor:

@page "/attribute-order-parent-2"

<AttributeOrderChild2 extra="10" />

父组件的呈现网页中的 <div> 包含 extra="10"：

<div extra="10" />

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