answer #1950 using BDN (#1951)

benchmarks/Dapper.Tests.Performance/Benchmarks.Linq2DB.cs

@@ -10,7 +10,7 @@ using System.ComponentModel;
 namespace Dapper.Tests.Performance
 {
     [Description("LINQ to DB")]
-    public class Linq2DBBenchmarks : BenchmarkBase
+    public class LinqToDBBenchmarks : BenchmarkBase // note To not 2 because the "2" confuses BDN CLI
     {
         private Linq2DBContext _dbContext;
 

benchmarks/Dapper.Tests.Performance/Benchmarks.Linq2Sql.cs

@@ -9,7 +9,7 @@ using System.Linq;
 namespace Dapper.Tests.Performance
 {
     [Description("LINQ to SQL")]
-    public class Linq2SqlBenchmarks : BenchmarkBase
+    public class LinqToSqlBenchmarks : BenchmarkBase // note To not 2 because the "2" confuses BDN CLI
     {
         private DataClassesDataContext Linq2SqlContext;
 

benchmarks/Dapper.Tests.Performance/Dapper.Tests.Performance.csproj

@@ -3,7 +3,7 @@
     <AssemblyName>Dapper.Tests.Performance</AssemblyName>
     <Description>Dapper Core Performance Suite</Description>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>net462;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net462;net5.0</TargetFrameworks>
     <IsTestProject>false</IsTestProject>
     <NoWarn>$(NoWarn);IDE0063;IDE0034;IDE0059;IDE0060</NoWarn>
   </PropertyGroup>

benchmarks/Dapper.Tests.Performance/DapperCacheImpact.cs

@@ -0,0 +1,39 @@
+using System.ComponentModel;
+using BenchmarkDotNet.Attributes;
+
+namespace Dapper.Tests.Performance
+{
+    [Description("Dapper cache impact")]
+    [MemoryDiagnoser]
+    public class DapperCacheImpact : BenchmarkBase
+    {
+        [GlobalSetup]
+        public void Setup() => BaseSetup();
+
+        private object args = new { Id = 42, Name = "abc" };
+
+        public class Foo
+        {
+            public int Id { get; set; }
+            public string Name { get; set; }
+        }
+
+        // note: custom BDN setup means [Params] is awkward; unroll manually instead
+        [Benchmark]
+        public void ExecuteNoParameters_Cache() => _connection.Execute(new CommandDefinition("select '42' as Id, 'abc' as Name", flags: CommandFlags.None));
+        [Benchmark]
+        public void ExecuteParameters_Cache() => _connection.Execute(new CommandDefinition("select @id as Id, @name as Name", args, flags: CommandFlags.None));
+        [Benchmark]
+        public void QueryFirstNoParameters_Cache() => _connection.QueryFirst<Foo>(new CommandDefinition("select '42' as Id, 'abc' as Name", flags: CommandFlags.None));
+        [Benchmark]
+        public void QueryFirstParameters_Cache() => _connection.QueryFirst<Foo>(new CommandDefinition("select @id as Id, @name as Name", args, flags: CommandFlags.None));
+        [Benchmark]
+        public void ExecuteNoParameters_NoCache() => _connection.Execute(new CommandDefinition("select '42' as Id, 'abc' as Name", flags: CommandFlags.NoCache));
+        [Benchmark]
+        public void ExecuteParameters_NoCache() => _connection.Execute(new CommandDefinition("select @id as Id, @name as Name", args, flags: CommandFlags.NoCache));
+        [Benchmark]
+        public void QueryFirstNoParameters_NoCache() => _connection.QueryFirst<Foo>(new CommandDefinition("select '42' as Id, 'abc' as Name", flags: CommandFlags.NoCache));
+        [Benchmark]
+        public void QueryFirstParameters_NoCache() => _connection.QueryFirst<Foo>(new CommandDefinition("select @id as Id, @name as Name", args, flags: CommandFlags.NoCache));
+    }
+}