MvcHtmlString in ASP.NET Core 6 MVC

I am migrating an application from ASP.NET MVC 5 running on .NET 4.8 to ASP.NET Core 6 MVC.

The MVC 5 application has the following:

 public static MvcHtmlString BuildColoredIconTag(string iconName, string color)
 {
	var icon = BuildInternalColoredIconTag(iconName, color);

	var htmlBuilder = new StringBuilder();

	htmlBuilder.Append(icon);

	var finalHtml = icon.ToString(TagRenderMode.Normal);

	return MvcHtmlString.Create(finalHtml);
}

I updated it to the following in the new application:

public static HtmlString BuildColoredIconTag(string iconName, string color)
{
	var icon = BuildInternalColoredIconTag(iconName, color);

	var htmlBuilder = new StringBuilder();

	htmlBuilder.Append(icon);

	var finalHtml = icon.TagRenderMode.ToString();

	return new HtmlString(finalHtml);
}

Is this correct or should I update it to something else? I cannot test it yet because I am adding other components.

I have the following in a partial .cshtml file, but I receive null reference warnings:

@IconExtensions.BuildColoredIconTag(ViewData["icon"].ToString(), "text-info")

What should I update it to?

It was caused by this line in your csproj file

<Nullable>enable</Nullable>

as mentioned in the document:

> By default, nullable annotation and warning contexts are disabled.
> That means that your existing code compiles without changes and
> without generating any new warnings. Beginning with .NET 6, new
> projects include the <Nullable>enable</Nullable> element in all
> project templates.

If you don't like it ,just disable it

<Nullable>disable</Nullable>

If you want to keep it without warning ,declearing iconName as string? or trying with ?? operater

like:

ViewData["icon"]?.ToString()??"DefaultIcon"

If you dont want to remove the new nullable stuff in VS, you could do something like this purely as an example, also I would convert it to an extension:

public static IHtmlString BuildColoredIconTag(this IHtmlHelper helper, string? iconName, string? color)
{
    if(string.IsNullOrEmpty(iconName)) return HtmlString.Empty;  // or throw

    if(string.IsNullOrEmpty(color)) return HtmlString.Empty; // or throw

    var icon = BuildInternalColoredIconTag(iconName, color);

    var htmlBuilder = new StringBuilder();

    htmlBuilder.Append(icon);

    var finalHtml = icon.TagRenderMode.ToString();

    return new HtmlString(finalHtml);
}

Then call like:

@Html.BuildColoredIconTag(ViewData["icon"].ToString(), "text-info")

And to simplify things even further you could change the method's signature to:

public static IHtmlString BuildColoredIconTag(this IHtmlHelper helper, object? iconName, string? color)
{
  if(iconName == null) {  return HtmlString.Empty; }
  
  ...

And then call with @Html.BuildColoredIconTag(ViewData["icon"], "text-info")