Added ToCLASSNAMEFirstOrDefault method generation. Fixed some minor test warnings

Author: alex-jitbit

MapDataReader.Tests/TestActualCode.cs

@@ -38,14 +38,14 @@ public class MyObject
 
 		public MyEnum Dude { get; set; }
 		public MyEnum? NullableDude { get; set; }
-		public string Name { get; set; }
+		public string? Name { get; set; }
 
 		public int GetOnly { get; } = 123; //property without public setter!
 
-		public byte[] ByeArray { get; set; }
-		public int[] IntArray { get; set; }
-		public string[] StringArray { get; set; }
-		public long[] LongArray { get; set; }
+		public byte[]? ByeArray { get; set; }
+		public int[]? IntArray { get; set; }
+		public string[]? StringArray { get; set; }
+		public long[]? LongArray { get; set; }
 	}
 
 	[TestClass]
@@ -205,6 +205,38 @@ public void TestDatatReader()
 			Assert.IsTrue(list[0].LaBoolissimmo == true);
 		}
 
+		[TestMethod]
+		public void TestDataReaderFirstOrDefault()
+		{
+			var dt = new DataTable();
+			dt.Columns.AddRange(new[] {
+				new DataColumn("ID", typeof(int)),
+				new DataColumn("Name", typeof(string)),
+			});
+			dt.Rows.Add(123, "first");
+			dt.Rows.Add(456, "second");
+
+			var result = dt.CreateDataReader().ToMyObjectFirstOrDefault();
+
+			Assert.IsNotNull(result);
+			Assert.IsTrue(result.Id == 123);
+			Assert.IsTrue(result.Name == "first");
+		}
+
+		[TestMethod]
+		public void TestDataReaderFirstOrDefault_Empty()
+		{
+			var dt = new DataTable();
+			dt.Columns.AddRange(new[] {
+				new DataColumn("ID", typeof(int)),
+				new DataColumn("Name", typeof(string)),
+			});
+
+			var result = dt.CreateDataReader().ToMyObjectFirstOrDefault();
+
+			Assert.IsNull(result);
+		}
+
 		[TestMethod]
 		public void TestBaseClassAssign()
 		{
@@ -237,7 +269,7 @@ public class BaseClass
 	[GenerateDataReaderMapper]
 	public class ChildClass : BaseClass
 	{
-		public string Name { get; set; }
+		public string? Name { get; set; }
 	}
 }
 

MapDataReader.Tests/TestGenerator.cs

@@ -78,7 +78,7 @@ private static Compilation CreateCompilation(string source)
 					MetadataReference.CreateFromFile(typeof(MapperGenerator).GetTypeInfo().Assembly.Location),
 					MetadataReference.CreateFromFile(typeof(IDataReader).GetTypeInfo().Assembly.Location),
 					MetadataReference.CreateFromFile(typeof(Enumerable).GetTypeInfo().Assembly.Location),
-					MetadataReference.CreateFromFile(Path.Combine(Path.GetDirectoryName(typeof(object).Assembly.Location), "System.Runtime.dll")),
+					MetadataReference.CreateFromFile(Path.Combine(Path.GetDirectoryName(typeof(object).Assembly.Location)!, "System.Runtime.dll")),
 					MetadataReference.CreateFromFile(AppDomain.CurrentDomain.GetAssemblies().Single(a => a.GetName().Name == "netstandard").Location)
 				},
 				new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));

MapDataReader/MapperGenerator.cs

@@ -3,16 +3,29 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 
 namespace MapDataReader
 {
+	/// <summary>
+	/// Mark a class with this attribute to generate a data reader mapper for it.
+	/// </summary>
 	[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
 	public class GenerateDataReaderMapperAttribute : Attribute
 	{
 	}
 
+	public static class DataReaderHelper
+	{
+		public static string[] GetUpperColumnNames(System.Data.IDataReader dr)
+		{
+			string[] columnNames = new string[dr.FieldCount];
+			for (int i = 0; i < columnNames.Length; i++)
+				columnNames[i] = dr.GetName(i).ToUpperInvariant();
+			return columnNames;
+		}
+	}
+
 	[Generator]
 	public class MapperGenerator : ISourceGenerator
 	{
@@ -86,10 +99,7 @@ private static void SetPropertyByUpperName(this {typeNodeSymbol.FullName()} targ
 								
 								if (dr.Read())
 								{{
-									string[] columnNames = new string[dr.FieldCount];
-									
-									for (int i = 0; i < columnNames.Length; i++)
-										columnNames[i] = dr.GetName(i).ToUpperInvariant();
+									string[] columnNames = DataReaderHelper.GetUpperColumnNames(dr);
 
 									do
 									{{
@@ -105,6 +115,27 @@ private static void SetPropertyByUpperName(this {typeNodeSymbol.FullName()} targ
 								}}
 								dr.Close();
 								return list;
+							}}
+
+							public static {typeNodeSymbol.FullName()} To{typeNode.Identifier}FirstOrDefault(this IDataReader dr)
+							{{
+								if (!dr.Read())
+								{{
+									dr.Close();
+									return default;
+								}}
+
+								string[] columnNames = DataReaderHelper.GetUpperColumnNames(dr);
+
+								var result = new {typeNodeSymbol.FullName()}();
+								for (int i = 0; i < columnNames.Length; i++)
+								{{
+									var value = dr[i];
+									if (value is DBNull) value = null;
+									SetPropertyByUpperName(result, columnNames[i], value);
+								}}
+								dr.Close();
+								return result;
 							}}";
 				}