Updates .yml file to support .net core

azure-pipelines.yml

@@ -16,6 +16,13 @@ variables:
   buildConfiguration: 'Release'
 
 steps:
+- task: UseDotNet@2
+  displayName: 'Install .NET Core sdk'
+  inputs:
+    packageType: sdk
+    version: 3.1.100
+    installationPath: $(Agent.ToolsDirectory)/dotnet
+    
 - task: NuGetToolInstaller@1
 
 - task: NuGetCommand@2