change .net version

NuGet.config

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+    <packageSources>
+        <clear />
+        <add key="NuGet.org" value="https://api.nuget.org/v3/index.json" />
+    </packageSources>
+    <solution>
+      <add key="disableSourceControlIntegration" value="true" />
+    </solution>
+</configuration>

Revit.Toolkit.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.29411.138
+# Visual Studio Version 17
+VisualStudioVersion = 17.4.33103.184
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CodeCave.Revit.Toolkit", "src\CodeCave.Revit.Toolkit.csproj", "{A6FB1B02-639B-4110-A525-899D7E2E36ED}"
 EndProject
@@ -16,6 +16,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		Directory.Build.targets = Directory.Build.targets
 		global.json = global.json
 		LICENSE.txt = LICENSE.txt
+		NuGet.config = NuGet.config
 		README.md = README.md
 		stylecop.json = stylecop.json
 		stylecop.ruleset = stylecop.ruleset

tests/CodeCave.Revit.Toolkit.Tests.csproj

@@ -1,13 +1,13 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="[16.*, 17.0)" />
-    <PackageReference Include="OpenCover" Version="4.6.*" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="[17.*, 18.0)" />
+    <PackageReference Include="OpenCover" Version="4.7.*" />
     <PackageReference Include="xunit" Version="2.4.*" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.*" />
   </ItemGroup>