Add source type namespace to usings if needed.

MapTo/MapToGenerator.cs

@@ -66,6 +66,7 @@ namespace MapTo
                 classModifiers: classSyntax.GetClassModifier(),  
                 className: classSyntax.GetClassName(),
                 properties: classSymbol.GetAllMembersOfType<IPropertySymbol>(),
+                destinationNamespace: destinationTypeSymbol.ContainingNamespace.Name,
                 destinationClassName: destinationTypeSymbol.Name,
                 destinationTypeProperties: destinationTypeSymbol.GetAllMembersOfType<IPropertySymbol>());
         }

MapTo/Models/MapModel.cs

@@ -6,12 +6,13 @@ namespace MapTo.Models
 {
     public class MapModel
     {
-        public MapModel(string? ns, string classModifiers, string className, IEnumerable<IPropertySymbol> properties, string destinationClassName, IEnumerable<IPropertySymbol> destinationTypeProperties)
+        public MapModel(string? ns, string classModifiers, string className, IEnumerable<IPropertySymbol> properties, string destinationNamespace, string destinationClassName, IEnumerable<IPropertySymbol> destinationTypeProperties)
         {
             Namespace = ns;
             ClassModifiers = classModifiers;
             ClassName = className;
             Properties = properties;
+            DestinationNamespace = destinationNamespace;
             DestinationClassName = destinationClassName;
             DestinationTypeProperties = destinationTypeProperties;
         }
@@ -24,6 +25,8 @@ namespace MapTo.Models
         
         public IEnumerable<IPropertySymbol> Properties { get; }
         
+        public string DestinationNamespace { get; }
+        
         public string DestinationClassName { get; }
         
         public IEnumerable<IPropertySymbol> DestinationTypeProperties { get; }

MapTo/SourceProvider.cs

@@ -47,7 +47,7 @@ namespace MapTo
 
             builder
                 .AppendFileHeader()
-                .GenerateUsings();
+                .GenerateUsings(model);
 
             // Namespace declaration
             builder
@@ -75,17 +75,22 @@ namespace MapTo
             return (builder.ToString(), $"{model.ClassName}.cs");
         }
 
-        private static StringBuilder GenerateUsings(this StringBuilder builder)
+        private static StringBuilder GenerateUsings(this StringBuilder builder, MapModel model)
         {
-            return builder
-                .AppendLine("using System;")
-                .AppendLine();
+            builder.AppendLine("using System;");
+
+            if (!string.IsNullOrWhiteSpace(model.DestinationNamespace) && model.Namespace != model.DestinationNamespace)
+            {
+                builder.AppendFormat("using {0};", model.DestinationNamespace).AppendLine();
+            }
+            
+            return builder.AppendLine();
         }
-        
+
         private static StringBuilder GenerateConstructor(this StringBuilder builder, MapModel model, out List<IPropertySymbol> mappedProperties)
         {
             var destinationClassParameterName = model.DestinationClassName.ToCamelCase();
-            
+
             builder
                 .PadLeft(Indent2)
                 .AppendFormat("public {0}({1} {2})", model.ClassName, model.DestinationClassName, destinationClassParameterName)
@@ -120,7 +125,7 @@ namespace MapTo
                 .AppendFormat("public static {0} From({1} {2})", model.ClassName, model.DestinationClassName, destinationClassParameterName)
                 .AppendOpeningBracket(Indent2)
                 .PadLeft(Indent3)
-                .AppendFormat("return {0} == null ? null : new {1}({0});", destinationClassParameterName, model.ClassName )
+                .AppendFormat("return {0} == null ? null : new {1}({0});", destinationClassParameterName, model.ClassName)
                 .AppendClosingBracket(Indent2);
         }
 

MapToTests/Tests.cs

@@ -1,4 +1,5 @@
 using System.Linq;
+using System.Text;
 using Shouldly;
 using Xunit;
 using Xunit.Abstractions;
@@ -196,12 +197,36 @@ namespace Test
             compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldContain(expectedResult.Trim());
         }
-
-        private static string GetSourceText(bool includeAttributeNamespace = false)
+        
+        [Fact]
+        public void When_SourceTypeHasDifferentNamespace_Should_AddToUsings()
         {
-            return  @$"
+            // Arrange
+            var source = GetSourceText(sourceClassNamespace: "Bazaar");
+            
+            const string expectedResult = @"
+// <auto-generated />
+using System;
+using Bazaar;
+";
+            
+            // Act
+            var (compilation, diagnostics) = CSharpGenerator.GetOutputCompilation(source);
+            
+            // Assert
+            diagnostics.ShouldBeSuccessful();
+            compilation.SyntaxTrees.Count().ShouldBe(3);
+            compilation.SyntaxTrees.Last().ToString().ShouldStartWith(expectedResult.Trim());
+        }
+
+        private static string GetSourceText(bool includeAttributeNamespace = false, string sourceClassNamespace = "Test")
+        {
+            var builder = new StringBuilder();
+            builder.AppendLine($@"
 namespace Test
 {{
+    {(sourceClassNamespace != "Test" && !includeAttributeNamespace ? $"using {sourceClassNamespace};": string.Empty)}
+
     {(includeAttributeNamespace ? "[MapTo.MapFrom(typeof(Baz))]" : "[MapFrom(typeof(Baz))]")}
     public partial class Foo
     {{
@@ -209,7 +234,12 @@ namespace Test
         public int Prop2 {{ get; }}
         public int Prop3 {{ get; }}
     }}
+}}
+");
 
+            builder.AppendLine($@"
+namespace {sourceClassNamespace}
+{{
     public class Baz 
     {{
         public int Prop1 {{ get; set; }}
@@ -217,7 +247,9 @@ namespace Test
         public int Prop3 {{ get; set; }}
     }}
 }}
-";
+");
+
+            return builder.ToString();
         }
     }
 }