/// <summary>
/// Projects query to given generic argument type.
/// For example: Converting Entity queries to DTO queries.
/// </summary>
/// <typeparam name="TOut">Target type.</typeparam>
/// <param name="query">The query.</param>
/// <param name="mapDefinitions">Map definitions (property mappings) for source and destination types.</param>
/// <returns>Projected query.</returns>
public static IQueryable <TOut> ProjectTo <TOut>(this IQueryable query, IMapDefinitionCollection mapDefinitions = null)
{
var projector = CreateProjector(query.ElementType, typeof(TOut), GetIncludes(query), mapDefinitions);
return((IQueryable <TOut>)query.Provider.CreateQuery(
Expression.Call(
typeof(Queryable), "Select",
new Type[] { query.ElementType, typeof(TOut) },
query.Expression, projector)
));
}
/// <summary>
/// Generates projector lambda for given generic argument types.
/// </summary>
/// <typeparam name="TIn">Source type.</typeparam>
/// <typeparam name="TOut">Target type.</typeparam>
/// <param name="includes">Navigation properties to include in projection.</param>
/// <param name="mapDefinitions">Map definitions (property mappings) for source and destination types.</param>
/// <returns>The reusable lambda expression.</returns>
public static Expression <Func <TIn, TOut> > CreateProjector <TIn, TOut>(IEnumerable <string> includes = null, IMapDefinitionCollection mapDefinitions = null)
{
return((Expression <Func <TIn, TOut> >)CreateProjector(typeof(TIn), typeof(TOut), includes, mapDefinitions));
}
/// <summary>
/// Creates projector object initializer for given types.
/// </summary>
/// <param name="inType">Source type.</param>
/// <param name="outType">Target type.</param>
/// <param name="includes">Navigation properties to include in projection.</param>
/// <param name="prmExp">ParameterExpression instance to point the source object.</param>
/// <returns>The reusable projector object initializer.</returns>
/// <param name="mapDefinitions">Map definitions (property mappings) for source and destination types.</param>
private static MemberInitExpression CreateAssigner(Type inType, Type outType, IEnumerable <string> includes,
IMapDefinitionCollection mapDefinitions, Expression prmExp)
{
var inProperties = GetMapFields(inType);
var outProperties = GetMapFields(outType, true);
IMapDefinition mapDefinition;
if (mapDefinitions != null)
{
mapDefinition = mapDefinitions.Resolve(inType, outType);
}
else
{
mapDefinition = null;
}
Dictionary <string, Tuple <MapMember, MapMember> > navigationMapping = new Dictionary <string, Tuple <MapMember, MapMember> >();
var memberBindings = new List <MemberBinding>();
foreach (var outProperty in outProperties)
{
string mappedInPropertyName;
if (mapDefinition != null)
{
if (!mapDefinition.Maps.TryGetValue(outProperty.Name, out mappedInPropertyName))
{
if (mapDefinition.OnlyExplicit)
{
continue;
}
mappedInPropertyName = outProperty.Name;
}
}
else
{
mappedInPropertyName = outProperty.Name;
}
var inProperty = inProperties.FirstOrDefault(p => p.Name == mappedInPropertyName);
if (inProperty != null)
{
if (inProperty.IsPrimitive)
{
var p1Exp = Expression.PropertyOrField(prmExp, inProperty.Name);
memberBindings.Add(Expression.Bind(outProperty.MemberInfo, p1Exp));
}
else
{
navigationMapping[inProperty.Name] = new Tuple <MapMember, MapMember>(inProperty, outProperty);
}
}
}
if (includes != null && includes.Any())
{
var includeGroups = includes
.Select(i => {
var idx = i.IndexOf(".");
string path, other;
if (idx > 0)
{
path = i.Substring(0, idx);
other = i.Substring(idx + 1);
}
else
{
path = i;
other = null;
}
return(new { path, other });
})
.GroupBy(i => i.path)
.Select(i => new { Property = i.Key, SubIncludes = i.Select(o => o.other).Where(o => o != null) })
.ToList();
foreach (var includeGroup in includeGroups)
{
Tuple <MapMember, MapMember> includeMapping;
if (!navigationMapping.TryGetValue(includeGroup.Property, out includeMapping))
{
continue;
}
var inIncludeProperty = includeMapping.Item1;
var outIncludeProperty = includeMapping.Item2;
var inIncludeType = inIncludeProperty.Type;
var outIncludeType = outIncludeProperty.Type;
var inIncludeEnumerableType = inIncludeType.GetInterfaces()
.FirstOrDefault(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEnumerable <>));
var outIncludeEnumerableType = outIncludeType.GetInterfaces()
.FirstOrDefault(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEnumerable <>));
if (inIncludeEnumerableType != null)
{
if (outIncludeEnumerableType == null)
{
throw new ArrayTypeMismatchException($"Navigation type mismatch for property {includeGroup.Property}");
}
inIncludeType = inIncludeEnumerableType.GetGenericArguments()[0];
outIncludeType = outIncludeEnumerableType.GetGenericArguments()[0];
}
else if (outIncludeEnumerableType != null)
{
throw new ArrayTypeMismatchException($"Navigation type mismatch for property {includeGroup.Property}");
}
Expression subProjector;
if (inIncludeEnumerableType != null)
{
subProjector = CreateProjector(inIncludeType, outIncludeType, includeGroup.SubIncludes, mapDefinitions);
var subPropExp = Expression.PropertyOrField(prmExp, includeGroup.Property);
subProjector = Expression.Call(typeof(Enumerable), "Select", new Type[] { inIncludeType, outIncludeType }, subPropExp, subProjector);
subProjector = Expression.Call(typeof(Enumerable), "ToList", new Type[] { outIncludeType }, subProjector);
}
else
{
var subPrmExp = Expression.MakeMemberAccess(prmExp, inIncludeProperty.MemberInfo);
subProjector = CreateAssigner(inIncludeType, outIncludeType, includeGroup.SubIncludes, mapDefinitions, subPrmExp);
}
memberBindings.Add(Expression.Bind(outIncludeProperty.MemberInfo, subProjector));
}
}
return(Expression.MemberInit(Expression.New(outType), memberBindings));
}
/// <summary>
/// Generates projector lambda expression for given types.
/// </summary>
/// <param name="inType">Source type.</param>
/// <param name="outType">Target type.</param>
/// <param name="includes">Navigation properties to include in projection.</param>
/// <returns>The reusable projector lambda expression.</returns>
/// <param name="mapDefinitions">Map definitions (property mappings) for source and destination types.</param>
public static LambdaExpression CreateProjector(Type inType, Type outType, IEnumerable <string> includes = null, IMapDefinitionCollection mapDefinitions = null)
{
var prmExp = Expression.Parameter(inType, "e");
var memberInit = CreateAssigner(inType, outType, includes, mapDefinitions, prmExp);
return(Expression.Lambda(memberInit, prmExp));
}