你快到了。
Design
这里的困难在于我们需要为未知属性构造一个表达式。比方说，当你想使用<user-phones asp-for=""/>在更高的层次上，考虑以下代码：
@model M0
@{
var M1 = GetM1ByMagic(M0);
}
<user-phones asp-for="@M1.M2....Mx.UserPhones">
</user-phones>
在标签助手中，我们可能假设每个属性的默认名称是UserPhones[<index>].<property-name>。但情况并非总是如此，用户可能希望将其更改为M0.M2....Mx.UserPhones[<index>].<property-name>。但是，不可能知道编译时会有多少层。
所以我们需要一个属性ExpressionFilter将默认表达式转换为目标表达式：
public class UserPhonesTagHelper : TagHelper
{
[HtmlAttributeName("expression-filter")]
public Func<string, string> ExpressionFilter { get; set; } = e => e;
// ...
}
The ExpressionFilter这是一个转换表达式字符串的简单委托。
显示代码
我只是复制您的大部分代码并进行一些更改：
public class UserPhonesTagHelper : TagHelper
{
private readonly IHtmlGenerator _htmlGenerator;
private const string ForAttributeName = "asp-for";
public IList<UserPhones> Phones { get; set; }
[ViewContext]
public ViewContext ViewContext { set; get; }
[HtmlAttributeName(ForAttributeName)]
public ModelExpression For { get; set; }
public UserPhonesTagHelper(IHtmlGenerator htmlGenerator)
{
_htmlGenerator = htmlGenerator;
}
[HtmlAttributeName("expression-filter")]
public Func<string, string> ExpressionFilter { get; set; } = e => e;
// a helper method that generate a label and input for some property
private TagBuilder GenerateSimpleInputForField( int index ,PropertyInfo pi)
{
var instance = Phones[index];// current instance of a single UserPhone
var name = pi.Name; // property name : e.g. "PhoneNumberId"
var v = pi.GetValue(instance);
var div = new TagBuilder("div");
div.AddCssClass("form-group");
var expression = this.ExpressionFilter(For.Name + $"[{index}].{name}");
var explorer = For.ModelExplorer.GetExplorerForExpression(typeof(IList<UserPhones>), o =>v);
var label = _htmlGenerator.GenerateLabel( ViewContext, explorer, expression, name, new { } );
div.InnerHtml.AppendHtml(label);
var input = _htmlGenerator.GenerateTextBox( ViewContext, explorer, expression, v, null, new { @class = "form-control" } );
div.InnerHtml.AppendHtml(input);
return div;
}
public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
{
output.TagName = "div";
output.TagMode = TagMode.StartTagAndEndTag;
var type = typeof(UserPhones);
PropertyInfo phoneId= type.GetProperty("UserPhoneId");
PropertyInfo phoneNumber= type.GetProperty("PhoneNumber");
for (int i = 0; i< Phones.Count();i++) {
var div1 = this.GenerateSimpleInputForField(i,phoneId);
var div2 = this.GenerateSimpleInputForField(i,phoneNumber);
output.Content.AppendHtml(div1);
output.Content.AppendHtml(div2);
}
}
}
-
The ProcessAsync()上面仅显示了标签和输入UserPhoneId and PhoneNumber场地。如果您想自动显示所有属性，您只需将方法更改为：
public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
{
output.TagName = "div";
output.TagMode = TagMode.StartTagAndEndTag;
for (int i = 0; i < Phones.Count(); i++)
{
var pis = typeof(UserPhones).GetProperties();
foreach (var pi in pis)
{
var div = this.GenerateSimpleInputForField(i, pi);
output.Content.AppendHtml(div);
}
}
}
-
某些字段的默认表达式字符串是通过以下方式生成的：
get_the_name_by('asp-for') +'[<index>]'+'<property-name>'
eg :AppUser.UserPhones[i].<property-name>
当然这并不适用于所有情况，我们可以定制自己的expression-filter根据需要转换表达式：
// use <user-phones> in view file :
// custom our own expression filter :
@{
var regex= new System.Text.RegularExpressions.Regex(@"...");
Func<string, string> expressionFilter = e => {
var m = regex.Match(e);
// ...
return m.Groups["expression"].Value;
};
}
<user-phones phones="@Model.AppUser.UserPhones"
asp-for="@Model.AppUser.UserPhones"
expression-filter="expressionFilter">
</user-phones>
测试用例
<div class="row">
@await Html.PartialAsync("_NameAndID", Model.AppUser)
</div>
<form method="post">
<div class="row">
<user-phones phones="@Model.AppUser.UserPhones" asp-for="@Model.AppUser.UserPhones" expression-filter="e => e.Substring(8)"></user-phones>
</div>
<button type="submit">submit</button>
</form>
第一部分由局部视图生成，第二部分由user-phones:
