Update dotnetcore.yml

.github/workflows/dotnetcore.yml

@@ -10,8 +10,8 @@ jobs:
     steps:
     - uses: actions/checkout@v1
     - name: Setup .NET Core
-      uses: actions/setup-dotnet@v1
+      uses: actions/setup-dotnet@v1.5.0
       with:
         dotnet-version: 3.1.100
     - name: Build with dotnet
-      run: dotnet build --configuration Release
+      run: dotnet build IoTSharp.sln --configuration Release