From ffb2baf956426a7b8453d010fc761cdfe429037c Mon Sep 17 00:00:00 2001
From: David Francis <david.francis@medfarsolutions.com>
Date: Wed, 4 Aug 2021 00:19:21 -0400
Subject: [PATCH] Use Bcl async interfaces to add async streams to standard 2.0

---
 Dapper.StrongName/Dapper.StrongName.csproj |  3 +-
 Dapper/Dapper.csproj                       |  3 +-
 Dapper/SqlMapper.AsyncStream.cs            | 54 +++++++++++++++++-----
 Dapper/SqlMapper.GridReader.AsyncStream.cs |  4 +-
 4 files changed, 48 insertions(+), 16 deletions(-)

diff --git a/Dapper.StrongName/Dapper.StrongName.csproj b/Dapper.StrongName/Dapper.StrongName.csproj
index 31a43f156..1ed89eecd 100644
--- a/Dapper.StrongName/Dapper.StrongName.csproj
+++ b/Dapper.StrongName/Dapper.StrongName.csproj
@@ -5,7 +5,7 @@
     <Title>Dapper (Strong Named)</Title>
     <Description>A high performance Micro-ORM supporting SQL Server, MySQL, Sqlite, SqlCE, Firebird etc..</Description>
     <Authors>Sam Saffron;Marc Gravell;Nick Craver</Authors>
-    <TargetFrameworks>net461;netstandard2.0;netstandard2.1;net5.0</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;net5.0</TargetFrameworks>
     <SignAssembly>true</SignAssembly>
     <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
   </PropertyGroup>
@@ -19,6 +19,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="5.0.0" />
     <PackageReference Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
   </ItemGroup>
 </Project>
diff --git a/Dapper/Dapper.csproj b/Dapper/Dapper.csproj
index 74b9efe09..d7031a1bd 100644
--- a/Dapper/Dapper.csproj
+++ b/Dapper/Dapper.csproj
@@ -5,7 +5,7 @@
     <PackageTags>orm;sql;micro-orm</PackageTags>
     <Description>A high performance Micro-ORM supporting SQL Server, MySQL, Sqlite, SqlCE, Firebird etc..</Description>
     <Authors>Sam Saffron;Marc Gravell;Nick Craver</Authors>
-    <TargetFrameworks>net461;netstandard2.0;netstandard2.1;net5.0</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;net5.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Folder Include="Properties\" />
@@ -16,6 +16,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="5.0.0" />
     <PackageReference Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
   </ItemGroup>
 </Project>
diff --git a/Dapper/SqlMapper.AsyncStream.cs b/Dapper/SqlMapper.AsyncStream.cs
index 5e328226d..3ba96cd2b 100644
--- a/Dapper/SqlMapper.AsyncStream.cs
+++ b/Dapper/SqlMapper.AsyncStream.cs
@@ -1,4 +1,4 @@
-#if NET5_0 || NETSTANDARD2_1
+#if NET5_0 || NETSTANDARD2_0
 using System;
 using System.Collections.Generic;
 using System.Data;
@@ -96,7 +96,10 @@ private static async IAsyncEnumerable<T> StreamAsync<T>(this IDbConnection cnn,
             var info = GetCacheInfo(identity, param, command.AddToCache);
             bool wasClosed = cnn.State == ConnectionState.Closed;
             var cancel = command.CancellationToken;
-            await using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
+#if NET5_0
+            await
+#endif
+            using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
             DbDataReader reader = null;
             try
             {
@@ -131,7 +134,10 @@ private static async IAsyncEnumerable<T> StreamAsync<T>(this IDbConnection cnn,
             }
             finally
             {
-                await using (reader) { /* dispose if non-null */ }
+#if NET5_0
+                await
+#endif
+                using (reader) { /* dispose if non-null */ }
                 if (wasClosed) cnn.Close();
             }
         }
@@ -392,8 +398,14 @@ private static async IAsyncEnumerable<TReturn> MultiMapStreamAsync<TFirst, TSeco
             try
             {
                 if (wasClosed) await cnn.TryOpenAsync(command.CancellationToken).ConfigureAwait(false);
-                await using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
-                await using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, cancel).ConfigureAwait(false);
+#if NET5_0
+                await
+#endif
+                using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
+#if NET5_0
+                await
+#endif
+                using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, cancel).ConfigureAwait(false);
                 if (!command.Buffered) wasClosed = false; // handing back open reader; rely on command-behavior
                 var results = MultiMapStreamImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(null, CommandDefinition.ForCallback(command.Parameters), map, splitOn, reader, identity, true);
 
@@ -451,8 +463,14 @@ private static async IAsyncEnumerable<TReturn> MultiMapStreamAsync<TReturn>(this
             try
             {
                 if (wasClosed) await cnn.TryOpenAsync(command.CancellationToken).ConfigureAwait(false);
-                await using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
-                await using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, cancel).ConfigureAwait(false);
+#if NET5_0
+                await
+#endif
+                using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
+#if NET5_0
+                await
+#endif
+                using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, cancel).ConfigureAwait(false);
                 var results = MultiMapAsyncImpl(null, default, types, map, splitOn, reader, identity, true);
 
                 var buffer = command.Buffered ? new List<TReturn>() : null;
@@ -523,12 +541,18 @@ private static async IAsyncEnumerable<TReturn> MultiMapStreamImpl<TFirst, TSecon
             {
                 try
                 {
-                    await using (ownedReader) { /* dispose if non-null */ }
+#if NET5_0
+                    await
+#endif
+                    using (ownedReader) { /* dispose if non-null */ }
                 }
                 finally
                 {
                     ownedCommand?.Parameters.Clear();
-                    await using (ownedCommand) { /* dispose if non-null */ }
+#if NET5_0
+                    await
+#endif
+                    using (ownedCommand) { /* dispose if non-null */ }
                     if (wasClosed) cnn.Close();
                 }
             }
@@ -590,16 +614,22 @@ private static async IAsyncEnumerable<TReturn> MultiMapAsyncImpl<TReturn>(this I
             {
                 try
                 {
-                    await using (ownedReader) { /* dispose if non-null */ }
+#if NET5_0
+                    await
+#endif
+                    using (ownedReader) { /* dispose if non-null */ }
                 }
                 finally
                 {
                     ownedCommand?.Parameters.Clear();
-                    await using (ownedCommand) { /* dispose if non-null */ }
+#if NET5_0
+                    await
+#endif
+                    using (ownedCommand) { /* dispose if non-null */ }
                     if (wasClosed) cnn.Close();
                 }
             }
         }
     }
 }
-#endif // NET5_0
+#endif // NET5_0 || NETSTANDARD2_0
diff --git a/Dapper/SqlMapper.GridReader.AsyncStream.cs b/Dapper/SqlMapper.GridReader.AsyncStream.cs
index dada96b16..59c43b5c3 100644
--- a/Dapper/SqlMapper.GridReader.AsyncStream.cs
+++ b/Dapper/SqlMapper.GridReader.AsyncStream.cs
@@ -1,4 +1,4 @@
-#if NET5_0 || NETSTANDARD2_1
+#if NET5_0 || NETSTANDARD2_0
 using System;
 using System.Collections.Generic;
 using System.Data;
@@ -97,4 +97,4 @@ private async IAsyncEnumerable<T> ReadStreamAsync<T>(int index, Func<IDataReader
         }
     }
 }
-#endif // NET5_0 || NETSTANDARD2_1
+#endif // NET5_0 || NETSTANDARD2_0