Quote due to #1183

Author: Chuxel

containers/dotnet-mssql/.devcontainer/Dockerfile

@@ -1,5 +1,5 @@
 # [Choice] .NET version: 6.0, 5.0, 3.1
-ARG VARIANT=6.0
+ARG VARIANT="6.0"
 FROM mcr.microsoft.com/vscode/devcontainers/dotnet:${VARIANT}-focal
 
 # [Choice] Node.js version: none, lts/*, 16, 14, 12, 10

containers/dotnet-mssql/.devcontainer/docker-compose.yml

@@ -7,7 +7,7 @@ services:
       dockerfile: Dockerfile
       args:
         # Update 'VARIANT' to pick a version of .NET: 3.1, 5.0, 6.0
-        VARIANT: 6.0
+        VARIANT: "6.0"
         # Optional version of Node.js
         NODE_VERSION: "lts/*"