Merge pull request #1575 from zqlovejyc/main

Author: NickCraver

Dapper/SqlMapper.GridReader.Async.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Data;
 using System.Data.Common;
+using System.Globalization;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -178,7 +179,7 @@ private Task<IEnumerable<T>> ReadAsyncImpl<T>(Type type, bool buffered)
                 else
                 {
                     var result = ReadDeferred<T>(gridIndex, deserializer.Func, type);
-                    if (buffered) result = result.ToList(); // for the "not a DbDataReader" scenario
+                    if (buffered) result = result?.ToList(); // for the "not a DbDataReader" scenario
                     return Task.FromResult(result);
                 }
             }
@@ -210,7 +211,9 @@ private async Task<T> ReadRowAsyncImplViaDbReader<T>(DbDataReader reader, Type t
                         deserializer = new DeserializerState(hash, GetDeserializer(type, reader, 0, -1, false));
                         cache.Deserializer = deserializer;
                     }
-                    result = (T)deserializer.Func(reader);
+
+                    result = ConvertTo<T>(deserializer.Func(reader));
+
                     if ((row & Row.Single) != 0 && await reader.ReadAsync(cancel).ConfigureAwait(false)) ThrowMultipleRows(row);
                     while (await reader.ReadAsync(cancel).ConfigureAwait(false)) { /* ignore subsequent rows */ }
                 }
@@ -230,7 +233,7 @@ private async Task<IEnumerable<T>> ReadBufferedAsync<T>(int index, Func<IDataRea
                     var buffer = new List<T>();
                     while (index == gridIndex && await reader.ReadAsync(cancel).ConfigureAwait(false))
                     {
-                        buffer.Add((T)deserializer(reader));
+                        buffer.Add(ConvertTo<T>(deserializer(reader)));
                     }
                     return buffer;
                 }

Dapper/SqlMapper.GridReader.cs

@@ -3,6 +3,8 @@
 using System.Data;
 using System.Linq;
 using System.Globalization;
+using System.Runtime.CompilerServices;
+
 namespace Dapper
 {
     public static partial class SqlMapper
@@ -159,7 +161,7 @@ private IEnumerable<T> ReadImpl<T>(Type type, bool buffered)
                 }
                 IsConsumed = true;
                 var result = ReadDeferred<T>(gridIndex, deserializer.Func, type);
-                return buffered ? result.ToList() : result;
+                return buffered ? result?.ToList() : result;
             }
 
             private T ReadRow<T>(Type type, Row row)
@@ -181,16 +183,9 @@ private T ReadRow<T>(Type type, Row row)
                         deserializer = new DeserializerState(hash, GetDeserializer(type, reader, 0, -1, false));
                         cache.Deserializer = deserializer;
                     }
-                    object val = deserializer.Func(reader);
-                    if (val == null || val is T)
-                    {
-                        result = (T)val;
-                    }
-                    else
-                    {
-                        var convertToType = Nullable.GetUnderlyingType(type) ?? type;
-                        result = (T)Convert.ChangeType(val, convertToType, CultureInfo.InvariantCulture);
-                    }
+
+                    result = ConvertTo<T>(deserializer.Func(reader));
+
                     if ((row & Row.Single) != 0 && reader.Read()) ThrowMultipleRows(row);
                     while (reader.Read()) { /* ignore subsequent rows */ }
                 }
@@ -360,18 +355,9 @@ private IEnumerable<T> ReadDeferred<T>(int index, Func<IDataReader, object> dese
             {
                 try
                 {
-                    var convertToType = Nullable.GetUnderlyingType(effectiveType) ?? effectiveType;
                     while (index == gridIndex && reader.Read())
                     {
-                        object val = deserializer(reader);
-                        if (val == null || val is T)
-                        {
-                            yield return (T)val;
-                        }
-                        else
-                        {
-                            yield return (T)Convert.ChangeType(val, convertToType, CultureInfo.InvariantCulture);
-                        }
+                        yield return ConvertTo<T>(deserializer(reader));
                     }
                 }
                 finally // finally so that First etc progresses things even when multiple rows
@@ -433,6 +419,14 @@ public void Dispose()
                 }
                 GC.SuppressFinalize(this);
             }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            private static T ConvertTo<T>(object value) => value switch
+            {
+                T typed => typed,
+                null or DBNull => default,
+                _ => (T)Convert.ChangeType(value, Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T), CultureInfo.InvariantCulture),
+            };
         }
     }
 }

tests/Dapper.Tests/AsyncTests.cs

@@ -240,6 +240,16 @@ public async Task TestMultiAsync()
             }
         }
 
+        [Fact]
+        public async Task TestMultiConversionAsync()
+        {
+            using (SqlMapper.GridReader multi = await connection.QueryMultipleAsync("select Cast(1 as BigInt) Col1; select Cast(2 as BigInt) Col2").ConfigureAwait(false))
+            {
+                Assert.Equal(1, multi.ReadAsync<int>().Result.Single());
+                Assert.Equal(2, multi.ReadAsync<int>().Result.Single());
+            }
+        }
+
         [Fact]
         public async Task TestMultiAsyncViaFirstOrDefault()
         {

tests/Dapper.Tests/QueryMultipleTests.cs

@@ -31,6 +31,16 @@ public void TestQueryMultipleBuffered()
             }
         }
 
+        [Fact]
+        public void TestMultiConversion()
+        {
+            using (SqlMapper.GridReader multi = connection.QueryMultiple("select Cast(1 as BigInt) Col1; select Cast(2 as BigInt) Col2"))
+            {
+                Assert.Equal(1, multi.Read<int>().Single());
+                Assert.Equal(2, multi.Read<int>().Single());
+            }
+        }
+
         [Fact]
         public void TestQueryMultipleNonBufferedIncorrectOrder()
         {