An abstraction over AutoMapper to map several sources into single destination.

IMapper.cs

	/// <summary>
	/// Type mapping api
	/// </summary>
	public interface IMapper
	{
		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <typeparam name="TSource">Source type.</typeparam>
		/// <typeparam name="TDestination">Destination type.</typeparam>
		/// <param name="source">The source.</param>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		TDestination Map<TSource, TDestination>(TSource source);

		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <typeparam name="TDestination">The type of the destination instance.</typeparam>
		/// <param name="source">The source instance.</param>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		TDestination MapTo<TDestination>(object source);

		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <param name="source">The source instance.</param>
		/// <returns>Fluent interface for mapping.</returns>
		IMapBuilder Map(object source);
	}

	/// <summary>
	/// Fluent interface for mapping.
	/// </summary>
	public interface IMapBuilder
	{
		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <param name="source">The source instance.</param>
		/// <returns>Fluent interface for mapping.</returns>
		IMapBuilder Map(object source);

		/// <summary>
		/// Maps the specified earlier source type instances to destination type instance.
		/// </summary>
		/// <typeparam name="TDestination">The type of the destination.</typeparam>
		/// <param name="destination">The destination object.</param>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		TDestination To<TDestination>(TDestination destination);

		/// <summary>
		/// Maps the specified earlier source type instances to destination type instance.
		/// </summary>
		/// <typeparam name="TDestination">The type of the destination.</typeparam>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		TDestination To<TDestination>();
	}

Mapper.cs

	/// <summary>
	/// Type mapping api
	/// </summary>
	public class Mapper : IMapper
	{
		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <typeparam name="TSource">Source type.</typeparam>
		/// <typeparam name="TDestination">Destination type.</typeparam>
		/// <param name="source">The source.</param>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		public TDestination Map<TSource, TDestination>(TSource source)
		{
			return MapTo<TDestination>(source);
		}

		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <typeparam name="TDestination">The type of the destination instance.</typeparam>
		/// <param name="source">The source instance.</param>
		/// <returns>
		/// Instance of destination type.
		/// </returns>
		public TDestination MapTo<TDestination>(object source)
		{
			return Map(source)
				.To<TDestination>();
		}

		/// <summary>
		/// Maps the specified source type instance to destination type instance.
		/// </summary>
		/// <param name="source">The source instance.</param>
		/// <returns>Fluent interface for mapping.</returns>
		public IMapBuilder Map(object source)
		{
			return new MapBuilder(source);
		}

		#region Internal types

		/// <summary>
		/// Fluent interface for mapping.
		/// </summary>
		internal class MapBuilder : IMapBuilder
		{
			private readonly List<object> sources = new List<object>();

			/// <summary>
			/// Initialises a new instance of the <see cref="MapBuilder"/> class.
			/// </summary>
			/// <param name="source">The source instance.</param>
			public MapBuilder(object source)
			{
				sources.Add(source);
			}

			/// <summary>
			/// Maps the specified source type instance to destination type instance.
			/// </summary>
			/// <param name="source">The source instance.</param>
			/// <returns>Fluent interface for mapping.</returns>
			public IMapBuilder Map(object source)
			{
				sources.Add(source);
				return this;
			}

			/// <summary>
			/// Maps the specified earlier source type instances to destination type instance.
			/// </summary>
			/// <typeparam name="TDestination">The type of the destination.</typeparam>
			/// <param name="destination">The destination object.</param>
			/// <returns>
			/// Instance of destination type.
			/// </returns>
			public TDestination To<TDestination>(TDestination destination)
			{
				sources.ForEach(source => Map(source, destination));
				return destination;
			}

			/// <summary>
			/// Maps the specified earlier source type instances to destination type instance.
			/// </summary>
			/// <typeparam name="TDestination">The type of the destination.</typeparam>
			/// <returns>
			/// Instance of destination type.
			/// </returns>
			public TDestination To<TDestination>()
			{
				return sources.Aggregate(default(TDestination), (destination, source) => Map(source, destination));
			}

			/// <summary>
			/// Maps specified earlier source type instances to destination type instance.
			/// </summary>
			/// <param name="destinationType">The type of the destination.</param>
			/// <returns>
			/// Instance of destination type.
			/// </returns>
			public object ToType(Type destinationType)
			{
				return sources.Aggregate<object, object>(null, (destination, source) => Map(source, destination, destinationType));
			}

			private TDestination Map<TDestination>(object source, TDestination destination)
			{
				return destination != null
					? (TDestination)AutoMapper.Mapper.Map(source, destination, source.GetType(), typeof(TDestination))
					: AutoMapper.Mapper.Map<TDestination>(source);
			}

			private object Map(object source, object destination, Type destinationType)
			{
				return destination != null
					? AutoMapper.Mapper.Map(source, destination, source.GetType(), destinationType)
					: AutoMapper.Mapper.Map(source, source.GetType(), destinationType);
			}
		}

		#endregion
	}

MapperTest.cs

	public class MapperTest
	{
		private readonly IMapper target;

		public MapperTest()
		{
			AutoMapper.Mapper.CreateMap<SourceA, Destination>();
			AutoMapper.Mapper.CreateMap<SourceB, Destination>();
			target = new Mapper();
		}

		[Fact]
		public void Map_MapsSourceToDestinationObject_viaMapBuilder()
		{
			// Arrange.
			var source = new SourceA { A = "a value" };
			Destination destination = new DestinationProxy();

			// Act.
			var result = target.Map(source).To(destination);

			// Assert.
			result.Should().BeSameAs(destination);
			Assert.Equal(source.A, result.A);
			result.A.Should().Be(source.A);
			result.B.Should().BeNull();
		}

		[Fact]
		public void Map_MapsSourceToDestinationType_viaMapBuilder()
		{
			// Arrange.
			var source = new SourceA { A = "a value" };

			// Act.
			var result = target.Map(source).To<Destination>();

			// Assert.
			result.A.Should().Be(source.A);
			result.B.Should().BeNull();
		}

		[Fact]
		public void Map_MapsManySourcesToDestinationObject_viaMapBuilder()
		{
			// Arrange.
			var sourceA = new SourceA { A = "a value" };
			var sourceB = new SourceB { B = "b value" };
			Destination destination = new DestinationProxy();

			// Act.
			var result = target.Map(sourceA).Map(sourceB).To(destination);

			// Assert.
			result.Should().BeSameAs(destination);
			result.A.Should().Be(sourceA.A);
			result.B.Should().Be(sourceB.B);
		}

		[Fact]
		public void Map_MapsManySourcesToDestinationType_viaMapBuilder()
		{
			// Arrange.
			var sourceA = new SourceA { A = "a value" };
			var sourceB = new SourceB { B = "b value" };

			// Act.
			var result = target.Map(sourceA).Map(sourceB).To<Destination>();

			// Assert.
			result.A.Should().Be(sourceA.A);
			result.B.Should().Be(sourceB.B);
		}

		[Fact]
		public void Map_MapsManySourcesToTypeOfDestination_viaMapBuilder()
		{
			// Arrange.
			var sourceA = new SourceA { A = "a value" };
			var sourceB = new SourceB { B = "b value" };

			// Act.
			var result = target.Map(sourceA).Map(sourceB).ToType(typeof(Destination));

			// Assert.
			result.Should().BeOfType<Destination>();
			var destination = (Destination)result;
			destination.A.Should().Be(sourceA.A);
			destination.B.Should().Be(sourceB.B);
		}

		[Fact]
		public void Map_MapsSourceToDestinationType()
		{
			// Arrange.
			var source = new SourceA { A = "a value" };

			// Act.
			var result = target.Map<SourceA, Destination>(source);

			// Assert.
			result.A.Should().Be(source.A);
			result.B.Should().BeNull();
		}

		[Fact]
		public void MapTo_MapsSourceToDestinationType()
		{
			// Arrange.
			var source = new SourceA { A = "a value" };

			// Act.
			var result = target.MapTo<Destination>(source);

			// Assert.
			result.A.Should().Be(source.A);
			result.B.Should().BeNull();
		}

		#region Internals

		private class SourceA
		{
			public string A { get; set; }
		}

		private class SourceB
		{
			public string B { get; set; }
		}

		private class Destination
		{
			public string A { get; private set; }
			public string B { get; private set; }
		}

		/// <summary>
		/// It is used to make sure that mapper works with proxies.
		/// </summary>
		private class DestinationProxy : Destination
		{
		}

		#endregion
	}

Getting following error after using classes as specified:
An object reference is required for the non-static field, method, or property 'Mapper.Map(object, object, Type, Type)'
I am looking a generic way to map single source from multiple destination.

Thanks.