Add error for sql bindings when .net 5 (#1259)

* add error for sql bindings when .net 5

* add test

* cleanup linq stuff and move out common code

src/Microsoft.SqlTools.ServiceLayer/AzureFunctions/AzureFunctionsUtils.cs

@@ -0,0 +1,46 @@
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.SqlTools.ServiceLayer.AzureFunctions
+{
+    internal static class AzureFunctionsUtils
+    {
+        public const string functionAttributeText = "FunctionName";
+        public const string net5FunctionAttributeText = "Function";
+
+        /// <summary>
+        /// Gets all the methods in the syntax tree with an Azure Function attribute
+        /// </summary>
+        public static IEnumerable<MethodDeclarationSyntax> GetMethodsWithFunctionAttributes(CompilationUnitSyntax root)
+        {
+            // Look for Azure Functions in the file
+            // Get all method declarations
+            IEnumerable<MethodDeclarationSyntax> methodDeclarations = root.DescendantNodes().OfType<MethodDeclarationSyntax>();
+
+            // .NET 5 is not currently supported for sql bindings, so an error should be returned if this file has .NET 5 style Azure Functions
+            if (HasNet5StyleAzureFunctions(methodDeclarations))
+            {
+                throw new Exception(SR.SqlBindingsNet5NotSupported);
+            }
+
+            // get all the method declarations with the FunctionName attribute
+            IEnumerable<MethodDeclarationSyntax> methodsWithFunctionAttributes = methodDeclarations.Where(md => md.AttributeLists.Where(a => a.Attributes.Where(attr => attr.Name.ToString().Equals(functionAttributeText)).Any()).Any());
+
+            return methodsWithFunctionAttributes;
+        }
+
+        /// <summary>
+        /// Checks if any of the method declarations have .NET 5 style Azure Function attributes
+        /// .NET 5 AFs use the Function attribute, while .NET 3.1 AFs use FunctionName attritube
+        /// </summary>
+        public static bool HasNet5StyleAzureFunctions(IEnumerable<MethodDeclarationSyntax> methodDeclarations)
+        {
+            // get all the method declarations with the Function attribute
+            return methodDeclarations.Any(md => md.AttributeLists.Any(al => al.Attributes.Any(attr => attr.Name.ToString().Equals(net5FunctionAttributeText))));
+        }
+    }
+}