Asp.net core使用Razor试图引擎编写TagHelper

之前使用wtm来进行快速开发

wtm框架见：

https://wtmdoc.walkingtec.cn/

其前端选择Layui的情况下有大量的TagHelper，大幅度提高了开发效率

 虽然已有的组件很丰富但也不能完全覆盖所有的需求，这个时候就需要自己写TagHelper。

参考了WTM源码，和微软官方文档

TagHelper虽然使用起来方便，但是大量的拼接字符串编写体验和可读性都不是很好。

理想的情况是能充分利用.net中强大的Razor引擎来编写TagHelper，从而更方便的进行组件复用。

可以从asp.net core中找到viewengine的使用方法

 以封装一个wangEditor为例

TagHelper:

using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;
using System;
using System.IO;
using WalkingTec.Mvvm.Core;
using WalkingTec.Mvvm.Core.Extensions;
using WalkingTec.Mvvm.TagHelpers.LayUI;


namespace TagHelpers
{
    [HtmlTargetElement("wt:wangeditor", Attributes = "field", TagStructure = TagStructure.WithoutEndTag)]
    public class WangEditorTagHelper : TagHelper
    {
        public WangEditorTagHelper(ICompositeViewEngine viewEngine,IHttpContextAccessor httpContextAccessor) 
        {
            _viewEngine = viewEngine;
            _httpContextAccessor = httpContextAccessor;
        }

        public ModelExpression Field { get; set; }
        public string Id { get; set; }

        public string Name { get; set; }

        public int Height { get; set; } = 300;


        private ICompositeViewEngine _viewEngine;
        private IHttpContextAccessor _httpContextAccessor;

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var viewEngineResult = _viewEngine.GetView("~/Views/Shared/Components/WangEditor/", "Default.cshtml", false);
            if (!viewEngineResult.Success)
            {
                throw new InvalidOperationException($"Couldn't find view /Shared/Components/WangEditor/Default.cshtml");
            }

            using (var sr = new StringWriter())
            {
                var viewContext = new ViewContext();
                viewContext.HttpContext = _httpContextAccessor.HttpContext;
                viewContext.ViewData = new ViewDataDictionary<WangEditorConfig>(new EmptyModelMetadataProvider(), new ModelStateDictionary())
                {
                    Model = new WangEditorConfig()
                    {
                        Id = Id ?? Utils.GetIdByName(Field?.ModelExplorer.Container.ModelType.Name + "." + Field?.Name),
                        Name = Name ?? Field?.Name,
                        Value = Field?.Model?.ToString(),
                        Height = Height
                    }
                };
                viewContext.Writer = sr;

                viewEngineResult.View.RenderAsync(viewContext).GetAwaiter().GetResult();
                output.TagName = "div";
                output.TagMode = TagMode.StartTagAndEndTag;
                output.Content.SetHtmlContent(sr.ToString());
            }
        }
    }

    public class WangEditorConfig
    {
        public string Id { get; set; }

        public string Name { get; set; }

        public string Value { get; set; }

        public int Height { get; set; }
    }
}

cshtml，使用razor视图引擎编写可读性就好了很多。

@using TagHelpers;
@model WangEditorConfig

<style>
    #@(Model.Id)-editor—wrapper {
          border: 1px solid #ccc;
    }

    #@(Model.Id)-toolbar-container {
        border-bottom: 1px solid #ccc;
    }

    #@(Model.Id)-editor-container {
        height: @(Model.Height)px;
    }
</style>

<div id="@(Model.Id)-editor—wrapper" class="layui-input-block">
    <div id="@(Model.Id)-toolbar-container"><!-- 工具栏 --></div>
    <div id="@(Model.Id)-editor-container"><!-- 编辑器 --></div>
    <input type="hidden" value="@Model.Value" name="@Model.Name" id="@(Model.Id)-hidden"/>
</div>

<script type="text/javascript">
    (function(){
        var wEditor = window.wangEditor;

        var editorConfig = {
            placeholder: '请输入...',
            onChange(editor) {
                var hidden = document.getElementById("@(Model.Id)-hidden");
                var html = editor.getHtml();
                hidden.value=html;
            }
        }

        var editor = wEditor.createEditor({
            selector: '#@(Model.Id)-editor-container',
            html: '@Html.Raw(Model.Value)',
            config: editorConfig,
            mode: 'default', // or 'simple'
        })

        var toolbarConfig = {}

        toolbarConfig.excludeKeys = [
            'insertVideo', 'insertImage'
        ];

        var toolbar = wEditor.createToolbar({
            editor,
            selector: '#@(Model.Id)-toolbar-container',
            config: toolbarConfig,
            mode: 'simple', // or 'simple'
        })

        
        console.log(toolbar.getConfig().toolbarKeys);
    }());
   
</script>