[Blazor] Incorrect DOM namespace used with children of SVG foreignObject

[akorchev]

Describe the bug

Blazor seems to always use the SVG namespace when updating DOM nodes that are children of a SVG element.

To Reproduce

Use this Blazor page

<svg width="100" height="100">
    <foreignObject x="0" y="0" width="100" height="100">
        <strong>foo</strong>
        <strong>@foo</strong>
    </foreignObject>
</svg>

@code {
    string foo = "foo";
}

When you render it the second <strong> disappears immediately.

The DOM node is still there though:

Further inspection reveals the cause of the problem. The namespace of the second <strong> node is SVG.

The first which works has XHTML as a namespace.

I think the first works because it is "static" content.

Further technical details

• ASP.NET Core version - 3.1.101
• Include the output of dotnet --info

.NET Core SDK (reflecting any global.json):
 Version:   3.1.101
 Commit:    b377529961

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  10.14
 OS Platform: Darwin
 RID:         osx.10.14-x64
 Base Path:   /usr/local/share/dotnet/sdk/3.1.101/

Host (useful for support):
  Version: 3.1.1
  Commit:  a1388f194c

.NET Core SDKs installed:
  2.1.2 [/usr/local/share/dotnet/sdk]
  2.1.302 [/usr/local/share/dotnet/sdk]
  2.1.400 [/usr/local/share/dotnet/sdk]
  2.1.403 [/usr/local/share/dotnet/sdk]
  2.1.500 [/usr/local/share/dotnet/sdk]
  2.2.105 [/usr/local/share/dotnet/sdk]
  3.1.101 [/usr/local/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.2 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.6 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.2 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.6 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.1 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.2 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.6 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

• The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version - VS Code 1.42.1

[javiercn]

@akorchev thanks for contacting us.

We currently don't properly support SVG. We have a separate issue tracking this work, so I'm going to close this one in favor of the tracking issue we already have.

#18271

[akorchev]

@javiercn Ouch. We've undertaken quite a big SVG related task (Radzen Blazor Chart). So far this is the only issue with SVG and Blazor. Do you know what the existing issues are?