asp.net MVC6 Implementing a tagbuilder class and get error on ".ToString"

Question

I am getting compile errors when attempting to implement the message class from Levelnis's Blog.

The class in question is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNet.Mvc.Rendering;

namespace Notifier.Helpers.MessageNotifier
{
    public class Message
    {
        public MessageSeverity Severity { get; set; }

        public string Text { get; set; }

        public string Generate()
        {
            var isDismissable = Severity != MessageSeverity.Danger;
            if (Severity == MessageSeverity.None) Severity = MessageSeverity.Info;
            var sb = new StringBuilder();
            var divTag = new TagBuilder("div");
            divTag.AddCssClass("alert fade in");
            divTag.AddCssClass("alert-" + Severity.ToString().ToLower());


            var spanTag = new TagBuilder("span");
            spanTag.MergeAttribute("id", "MessageContent");

            if (isDismissable)
            {
                divTag.AddCssClass("alert-dismissable");
            }

            sb.Append(divTag.ToString(TagRenderMode.StartTag));

            if (isDismissable)
            {
                var buttonTag = new TagBuilder("button");
                buttonTag.MergeAttribute("class", "close");
                buttonTag.MergeAttribute("data-dismiss", "alert");
                buttonTag.MergeAttribute("aria-hidden", "true");
                buttonTag.InnerHtml = "×";
                sb.Append(buttonTag.ToString(TagRenderMode.Normal));
            }

            sb.Append(spanTag.ToString(TagRenderMode.StartTag));
            sb.Append(Text);
            sb.Append(spanTag.ToString(TagRenderMode.EndTag));
            sb.Append(divTag.ToString(TagRenderMode.EndTag));

            return sb.ToString();
        }
    }
}

I am getting two errors - the first relates to ".ToString" on the line:

sb.Append(divTag.ToString(TagRenderMode.StartTag));

and it says:

No overload for method 'ToString' takes 1 arguments

The second error relates to the line:

buttonTag.InnerHtml = "×";

and it says:

Property or indexer 'TagBuilder.InnerHtml' cannot be assigned to -- it is read only

I have had a look at the documentation and other posts but so far I have not found anything that can help me modify this to compile correctly...

Are these methods implemented differently in Asp.net-core and if not can someone suggest another way of doing these lines?

Answer 1

This was all to do with implementing a way of placing messages on the subsequent page - initially using Levilnis's Blog.

Not able to implement this without issues I stepped back and looked for another way of doing this. I used an approach presented by Mister James and in particular using a baseController to hold all my possible messages. I simplified it a bit as I didn't need to run multiple messages - just one per page.

public class BaseController : Controller
{
    public void Success(string message, bool dismissable = false)
    {
        AddAlert(AlertStyles.Success, message, dismissable);
    }

    public void Information(string message, bool dismissable = false)
    {
        AddAlert(AlertStyles.Information, message, dismissable);
    }

    public void Warning(string message, bool dismissable = false)
    {
        AddAlert(AlertStyles.Warning, message, dismissable);
    }

    public void Danger(string message, bool dismissable = false)
    {
        AddAlert(AlertStyles.Danger, message, dismissable);
    }

    private void AddAlert(string alertStyle, string message, bool dismissable)
    {
        var alert = new Alert
        {
            AlertStyle = alertStyle,
            Message = message,
            Dismissable = dismissable
        };

         TempData.Put(Alert.TempDataKey, alert);
    }

}

There was a wrinkle in that you cannot, in MVC6, send complex objects using Tempdata. This was solved using @Hem's answer in this Stackoverflow question where he suggests using an extension that converts the complex object into a json string. For this to work I did have t oadd the using "using Newtonsoft.Json;".

public static class TempDataExtensions
{
    public static void Put<T>(this ITempDataDictionary tempData, string key, T value) where T : class
    {
        tempData[key] = JsonConvert.SerializeObject(value);
    }

    public static T Get<T>(this ITempDataDictionary tempData, string key) where T : class
    {
        object o;
        tempData.TryGetValue(key, out o);
        return o == null ? null : JsonConvert.DeserializeObject<T>((string)o);
    }
}

This now works like a charm.

Answer 2

It seems TagBuilder does not work the same in MVC6 as it was in MVC5.

Instead of the ToString() method use StringWriter and the WriteTo() method as below:

StringBuilder result = new StringBuilder();
TagBuilder tag = new TagBuilder("a");
tag.AddCssClass("btn btn-default");  
using (var writer = new StringWriter())
{
  tag.WriteTo(writer, HtmlEncoder.Default);
  result.Append(writer.ToString());
}  

To set the InnerHtml use the Append() method as below:

tag.InnerHtml.Append(i.ToString()); 

This way it worked for me.