Downgrade Functions V1 .NET version to net461 (#1257)

At one point, we upgraded the full framework target framework from
net461 to net471 to reduce package size for our .NET Standard packages,
as well as to utilize some new language features. This has caused two
problems.

1. When Functions V1 customers target net462, they pull in the
netstandard2.0 version of the dll, which is meant for Functions V2/V3
customers.

2. Using any 4.7 or greater release for Functions V1 breaks when using
Microsoft.NET.Sdk.Functions 1.0.30 or greater, due to some conditional
logic relying on #if NET46. Unfortunately, this version of that package
is required to use Microsoft.Azure.WebJobs 2.3.0 instead of 2.2.0.

This PR reverts to net461 to avoid these issues, as well as some
required code changes to make it compatible with this older version.

src/WebJobs.Extensions.DurableTask/EntityScheduler/EntityId.cs

@@ -11,6 +11,8 @@ namespace Microsoft.Azure.WebJobs.Extensions.DurableTask
     /// </summary>
     public struct EntityId : IEquatable<EntityId>, IComparable
     {
+        private string schedulerId;
+
         /// <summary>
         /// Create an entity id for an entity.
         /// </summary>
@@ -25,6 +27,7 @@ public EntityId(string entityName, string entityKey)
 
             this.EntityName = entityName.ToLowerInvariant();
             this.EntityKey = entityKey ?? throw new ArgumentNullException(nameof(entityKey), "Invalid entity id: entity key must not be null.");
+            this.schedulerId = GetSchedulerId(this.EntityName, this.EntityKey);
         }
 
         /// <summary>
@@ -41,7 +44,12 @@ public EntityId(string entityName, string entityKey)
 
         internal static string GetSchedulerIdFromEntityId(EntityId entityId)
         {
-            return $"@{entityId.EntityName}@{entityId.EntityKey}";
+            return GetSchedulerId(entityId.EntityName, entityId.EntityKey);
+        }
+
+        private static string GetSchedulerId(string entityName, string entityKey)
+        {
+            return $"@{entityName}@{entityKey}";
         }
 
         internal static string GetSchedulerIdPrefixFromEntityName(string entityName)
@@ -60,7 +68,13 @@ internal static EntityId GetEntityIdFromSchedulerId(string schedulerId)
         /// <inheritdoc/>
         public override string ToString()
         {
-            return GetSchedulerIdFromEntityId(this);
+            // The scheduler id could be null if the object was deserialized.
+            if (this.schedulerId == null)
+            {
+                this.schedulerId = GetSchedulerIdFromEntityId(this);
+            }
+
+            return this.schedulerId;
         }
 
         /// <inheritdoc/>
@@ -72,21 +86,20 @@ public override bool Equals(object obj)
         /// <inheritdoc/>
         public bool Equals(EntityId other)
         {
-            return (this.EntityName, this.EntityKey).Equals((other.EntityName, other.EntityKey));
+            return this.ToString().Equals(other.ToString());
         }
 
         /// <inheritdoc/>
         public override int GetHashCode()
         {
-            return (this.EntityName, this.EntityKey).GetHashCode();
+            return this.ToString().GetHashCode();
         }
 
         /// <inheritdoc/>
         public int CompareTo(object obj)
         {
             var other = (EntityId)obj;
-            return ((IComparable)(this.EntityKey, this.EntityName))
-                      .CompareTo((other.EntityKey, other.EntityName));
+            return this.ToString().CompareTo(other.ToString());
         }
     }
 }

src/WebJobs.Extensions.DurableTask/Options/AzureStorageOptions.cs

@@ -163,7 +163,8 @@ internal bool IsSanitizedHubName(string hubName, out string sanitizedHubName)
             // a number. If it does, prepend "t" to the beginning.
             if (char.IsNumber(validHubNameCharacters.First()))
             {
-                validHubNameCharacters = validHubNameCharacters.Prepend('t');
+                validHubNameCharacters = validHubNameCharacters.ToList();
+                ((List<char>)validHubNameCharacters).Insert(0, 't');
             }
 
             sanitizedHubName = new string(validHubNameCharacters

src/WebJobs.Extensions.DurableTask/WebJobs.Extensions.DurableTask.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net471</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net461</TargetFrameworks>
     <AssemblyName>Microsoft.Azure.WebJobs.Extensions.DurableTask</AssemblyName>
     <RootNamespace>Microsoft.Azure.WebJobs.Extensions.DurableTask</RootNamespace>
     <MajorVersion>2</MajorVersion>
@@ -11,6 +11,7 @@
     <FileVersion>$(MajorVersion).$(MinorVersion).$(PatchVersion)</FileVersion>
     <AssemblyVersion>$(MajorVersion).0.0.0</AssemblyVersion>
     <Company>Microsoft Corporation</Company>
+    <LangVersion>7.3</LangVersion>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>..\..\sign.snk</AssemblyOriginatorKeyFile>
     <PublishRepositoryUrl>true</PublishRepositoryUrl>

test/Common/TestOrchestrations.cs

@@ -467,7 +467,7 @@ public static DurableHttpRequest ConvertTestRequestToDurableHttpRequest(TestDura
                     StringValues stringValues;
                     if (testHeaders.TryGetValue(header.Key, out stringValues))
                     {
-                        stringValues.Append(header.Value);
+                        stringValues = StringValues.Concat(stringValues, header.Value);
                         testHeaders[header.Key] = stringValues;
                     }
                     else

test/FunctionsV1/WebJobs.Extensions.DurableTask.Tests.V1.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net471</TargetFramework>
+    <TargetFramework>net461</TargetFramework>
     <Company>Microsoft Corporation</Company>
     <NoWarn>SA0001;SA1600;SA1615</NoWarn>
     <SignAssembly>true</SignAssembly>