Add WithVariable server extension method

Author: waxtell

.github/workflows/build.yml

@@ -12,6 +12,6 @@ jobs:
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 3.1.100
+        dotnet-version: 7.0.x
     - name: Build with dotnet
       run: dotnet build --configuration Release

SampleApp9000/SampleApp9000.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>