C# TagHelperOutput.MergeAttributes方法代码示例

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var builder = new TagBuilder("img");
            builder.Attributes["src"] = "/pictures/" + UrlHelperThumbnailExtensions.GetThumbnail(null, Src, Size);

            output.MergeAttributes(builder);
        }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var builder = new TagBuilder("li");
            if (ViewContext.ActionDescriptor.RouteValues["controller"] == Controller)
                builder.AddCssClass("active");

            output.MergeAttributes(builder);
        }

		/// <summary>
		///     Synchronously executes the <see cref="TagHelper" /> with the given <paramref name="context" /> and
		///     <paramref name="output" />.
		/// </summary>
		/// <param name="context">Contains information associated with the current HTML tag.</param>
		/// <param name="output">A stateful HTML element used to generate an HTML tag.</param>
		public override void Process(TagHelperContext context, TagHelperOutput output)
		{
			// Generate the list.
			var selectListItems = GenerateListForEnumType();

			// Get current value for model expression.
			var currentValues = Generator.GetCurrentValues(ViewContext, EnumFor.ModelExplorer, EnumFor.Name, false);


			var tag = Generator.GenerateSelect(ViewContext, EnumFor?.ModelExplorer, null, EnumFor?.Name, selectListItems,
				currentValues, false,
				null);

			if (tag != null)
			{
				output.MergeAttributes(tag);
				output.PostContent.AppendHtml(tag.InnerHtml);
			}
		}

        /// <inheritdoc />
        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
        public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            var tagBuilder = Generator.GenerateLabel(
                ViewContext,
                For.ModelExplorer,
                For.Name,
                labelText: null,
                htmlAttributes: null);

            if (tagBuilder != null)
            {
                output.MergeAttributes(tagBuilder);

                // We check for whitespace to detect scenarios such as:
                // <label for="Name">
                // </label>
                if (!output.IsContentModified)
                {
                    var childContent = await output.GetChildContentAsync();

                    if (childContent.IsEmptyOrWhiteSpace)
                    {
                        // Provide default label text since there was nothing useful in the Razor source.
                        output.Content.SetHtmlContent(tagBuilder.InnerHtml);
                    }
                    else
                    {
                        output.Content.SetHtmlContent(childContent);
                    }
                }
            }
        }

//.........这里部分代码省略.........
            var antiforgeryDefault = true;

            // If "action" is already set, it means the user is attempting to use a normal <form>.
            if (output.Attributes.ContainsName(HtmlActionAttributeName))
            {
                if (Action != null || Controller != null || Area != null || Route != null || RouteValues.Count != 0)
                {
                    // User also specified bound attributes we cannot use.
                    throw new InvalidOperationException(
                        Resources.FormatFormTagHelper_CannotOverrideAction(
                            "<form>",
                            HtmlActionAttributeName,
                            ActionAttributeName,
                            ControllerAttributeName,
                            AreaAttributeName,
                            RouteAttributeName,
                            RouteValuesPrefix));
                }

                // User is using the FormTagHelper like a normal <form> tag. Antiforgery default should be false to
                // not force the antiforgery token on the user.
                antiforgeryDefault = false;
            }
            else
            {
                IDictionary<string, object> routeValues = null;
                if (_routeValues != null && _routeValues.Count > 0)
                {
                    // Convert from Dictionary<string, string> to Dictionary<string, object>.
                    routeValues = new Dictionary<string, object>(_routeValues.Count, StringComparer.OrdinalIgnoreCase);
                    foreach (var routeValue in _routeValues)
                    {
                        routeValues.Add(routeValue.Key, routeValue.Value);
                    }
                }

                if (Area != null)
                {
                    if (routeValues == null)
                    {
                        routeValues = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
                    }

                    // Unconditionally replace any value from asp-route-area. 
                    routeValues["area"] = Area;
                }

                TagBuilder tagBuilder;
                if (Route == null)
                {
                    tagBuilder = Generator.GenerateForm(
                        ViewContext,
                        Action,
                        Controller,
                        routeValues,
                        method: null,
                        htmlAttributes: null);
                }
                else if (Action != null || Controller != null)
                {
                    // Route and Action or Controller were specified. Can't determine the action attribute.
                    throw new InvalidOperationException(
                        Resources.FormatFormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified(
                            "<form>",
                            RouteAttributeName,
                            ActionAttributeName,
                            ControllerAttributeName,
                            HtmlActionAttributeName));
                }
                else
                {
                    tagBuilder = Generator.GenerateRouteForm(
                        ViewContext,
                        Route,
                        routeValues,
                        method: null,
                        htmlAttributes: null);
                }

                if (tagBuilder != null)
                {
                    output.MergeAttributes(tagBuilder);
                    output.PostContent.AppendHtml(tagBuilder.InnerHtml);
                }

                if (string.Equals(Method, FormMethod.Get.ToString(), StringComparison.OrdinalIgnoreCase))
                {
                    antiforgeryDefault = false;
                }
            }

            if (Antiforgery ?? antiforgeryDefault)
            {
                var antiforgeryTag = Generator.GenerateAntiforgery(ViewContext);
                if (antiforgeryTag != null)
                {
                    output.PostContent.AppendHtml(antiforgeryTag);
                }
            }
        }

        /// <inheritdoc />
        /// <remarks>Does nothing if <see cref="ValidationSummary"/> is <see cref="ValidationSummary.None"/>.</remarks>
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            if (ValidationSummary == ValidationSummary.None)
            {
                return;
            }

            var tagBuilder = Generator.GenerateValidationSummary(
                ViewContext,
                excludePropertyErrors: ValidationSummary == ValidationSummary.ModelOnly,
                message: null,
                headerTag: null,
                htmlAttributes: null);
            if (tagBuilder != null)
            {
                output.MergeAttributes(tagBuilder);
                output.PostContent.AppendHtml(tagBuilder.InnerHtml);
            }
        }

//.........这里部分代码省略.........
        /// </exception>
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            // Pass through attributes that are also well-known HTML attributes. Must be done prior to any copying
            // from a TagBuilder.
            if (InputTypeName != null)
            {
                output.CopyHtmlAttribute("type", context);
            }

            if (Value != null)
            {
                output.CopyHtmlAttribute(nameof(Value), context);
            }

            // Note null or empty For.Name is allowed because TemplateInfo.HtmlFieldPrefix may be sufficient.
            // IHtmlGenerator will enforce name requirements.
            var metadata = For.Metadata;
            var modelExplorer = For.ModelExplorer;
            if (metadata == null)
            {
                throw new InvalidOperationException(Resources.FormatTagHelpers_NoProvidedMetadata(
                    "<input>",
                    ForAttributeName,
                    nameof(IModelMetadataProvider),
                    For.Name));
            }

            string inputType;
            string inputTypeHint;
            if (string.IsNullOrEmpty(InputTypeName))
            {
                // Note GetInputType never returns null.
                inputType = GetInputType(modelExplorer, out inputTypeHint);
            }
            else
            {
                inputType = InputTypeName.ToLowerInvariant();
                inputTypeHint = null;
            }

            // inputType may be more specific than default the generator chooses below.
            if (!output.Attributes.ContainsName("type"))
            {
                output.Attributes.SetAttribute("type", inputType);
            }

            TagBuilder tagBuilder;
            switch (inputType)
            {
                case "checkbox":
                    GenerateCheckBox(modelExplorer, output);
                    return;

                case "hidden":
                    tagBuilder = Generator.GenerateHidden(
                        ViewContext,
                        modelExplorer,
                        For.Name,
                        value: For.Model,
                        useViewData: false,
                        htmlAttributes: null);
                    break;

                case "password":
                    tagBuilder = Generator.GeneratePassword(
                        ViewContext,
                        modelExplorer,
                        For.Name,
                        value: null,
                        htmlAttributes: null);
                    break;

                case "radio":
                    tagBuilder = GenerateRadio(modelExplorer);
                    break;

                default:
                    tagBuilder = GenerateTextBox(modelExplorer, inputTypeHint, inputType);
                    break;
            }

            if (tagBuilder != null)
            {
                // This TagBuilder contains the one <input/> element of interest. Since this is not the "checkbox"
                // special-case, output is a self-closing element no longer guaranteed.
                output.MergeAttributes(tagBuilder);
                output.Content.AppendHtml(tagBuilder.InnerHtml);
            }
        }

        /// <inheritdoc />
        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            // Ensure GenerateSelect() _never_ looks anything up in ViewData.
            var items = Items ?? Enumerable.Empty<SelectListItem>();

            if (For == null)
            {
                var options = Generator.GenerateGroupsAndOptions(optionLabel: null, selectList: items);
                output.PostContent.AppendHtml(options);
                return;
            }

            var tagBuilder = Generator.GenerateSelect(
                ViewContext,
                For.ModelExplorer,
                optionLabel: null,
                expression: For.Name,
                selectList: items,
                currentValues: _currentValues,
                allowMultiple: _allowMultiple,
                htmlAttributes: null);

            if (tagBuilder != null)
            {
                output.MergeAttributes(tagBuilder);
                output.PostContent.AppendHtml(tagBuilder.InnerHtml);
            }
        }

        /// <inheritdoc />
        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            var tagBuilder = Generator.GenerateTextArea(
                ViewContext,
                For.ModelExplorer,
                For.Name,
                rows: 0,
                columns: 0,
                htmlAttributes: null);

            if (tagBuilder != null)
            {
                // Overwrite current Content to ensure expression result round-trips correctly.
                output.Content.SetHtmlContent(tagBuilder.InnerHtml);

                output.MergeAttributes(tagBuilder);
            }
        }