OData

AutoMapper extentions for mapping expressions (OData)

To use, configure using the configuration helper method:

varmapper=newMapper(newMapperConfiguration(cfg =>{cfg.AddExpressionMapping();// Rest of your configuration},loggerFactory));// or if using the MS Ext DI:services.AddAutoMapper(cfg =>{cfg.AddExpressionMapping();},/* assemblies with profiles */);

DTO Queries

Expression Mapping also supports writing queries against the mapped objects. Take the following source and destination types:

publicclassUser{publicintId{get;set;}publicstringName{get;set;}}publicclassRequest{publicintId{get;set;}publicintAssigneeId{get;set;}publicUserAssignee{get;set;}}publicclassUserDTO{publicintId{get;set;}publicstringName{get;set;}}publicclassRequestDTO{publicintId{get;set;}publicUserDTOAssignee{get;set;}}

We can write LINQ expressions against the DTO collections.

ICollection<RequestDTO>requests=[.. context.Request.GetQuery1<RequestDTO,Request>(mapper, r =>r.Id>0&&r.Id<3,null,[r =>r.Assignee])];ICollection<UserDTO>users=[.. context.User.GetQuery1<UserDTO,User>(mapper, u =>u.Id>0&&u.Id<4, q =>q.OrderBy(u =>u.Name))];intcount=awaitcontext.Request.Query<RequestDTO,Request,int,int>(mapper, q =>q.Count(r =>r.Id>1));

The methods below map the DTO query expresions to the equivalent data query expressions. The call to IMapper.Map converts the data query results back to the DTO (or model) object types. The call to IMapper.ProjectTo converts the data query to a DTO (or model) query.

staticclassExtensions{internalstaticasyncTask<TModelResult>Query<TModel,TData,TModelResult,TDataResult>(thisIQueryable<TData>query,IMappermapper,Expression<Func<IQueryable<TModel>,TModelResult>>queryFunc)whereTData:class{//Map the expressionsFunc<IQueryable<TData>,TDataResult>mappedQueryFunc=mapper.MapExpression<Expression<Func<IQueryable<TData>,TDataResult>>>(queryFunc).Compile();//execute the queryreturnmapper.Map<TDataResult,TModelResult>(mappedQueryFunc(query));}//This example compiles the queryable expression.internalstaticIQueryable<TModel>GetQuery1<TModel,TData>(thisIQueryable<TData>query,IMappermapper,Expression<Func<TModel,bool>>filter=null,Expression<Func<IQueryable<TModel>,IQueryable<TModel>>>queryableExpression=null,IEnumerable<Expression<Func<TModel,object>>>expansions=null){Func<IQueryable<TData>,IQueryable<TData>>mappedQueryDelegate=mapper.MapExpression<Expression<Func<IQueryable<TData>,IQueryable<TData>>>>(queryableExpression)?.Compile();if(filter!=null)query=query.Where(mapper.MapExpression<Expression<Func<TData,bool>>>(filter));returnmappedQueryDelegate!=null?mapper.ProjectTo(mappedQueryDelegate(query),null,GetExpansions()):mapper.ProjectTo(query,null,GetExpansions());Expression<Func<TModel,object>>[]GetExpansions()=>expansions?.ToArray()??[];}//This example updates IQueryable<TData>.Expression with the mapped queryable expression argument.internalstaticIQueryable<TModel>GetQuery2<TModel,TData>(thisIQueryable<TData>query,IMappermapper,Expression<Func<TModel,bool>>filter=null,Expression<Func<IQueryable<TModel>,IQueryable<TModel>>>queryableExpression=null,IEnumerable<Expression<Func<TModel,object>>>expansions=null){Expression<Func<IQueryable<TData>,IQueryable<TData>>>mappedQueryExpression=mapper.MapExpression<Expression<Func<IQueryable<TData>,IQueryable<TData>>>>(queryableExpression);if(filter!=null)query=query.Where(mapper.MapExpression<Expression<Func<TData,bool>>>(filter));if(mappedQueryExpression!=null){varqueryableExpressionBody=GetUnconvertedExpression(mappedQueryExpression.Body);queryableExpressionBody=ReplaceParameter(queryableExpressionBody,mappedQueryExpression.Parameters[0],query.Expression);query=query.Provider.CreateQuery<TData>(queryableExpressionBody);}returnmapper.ProjectTo(query,null,GetExpansions());Expression<Func<TModel,object>>[]GetExpansions()=>expansions?.ToArray()??[];staticExpressionGetUnconvertedExpression(Expressionexpression)=>expression.NodeTypeswitch{ExpressionType.Convert or ExpressionType.ConvertChecked or ExpressionType.TypeAs=>GetUnconvertedExpression(((UnaryExpression)expression).Operand),
_ =>expression,};ExpressionReplaceParameter(Expressionexpression,ParameterExpressionsource,Expressiontarget)=>newParameterReplacer(source,target).Visit(expression);}classParameterReplacer(ParameterExpressionsource,Expressiontarget):ExpressionVisitor{privatereadonlyParameterExpression_source=source;privatereadonlyExpression_target=target;protectedoverrideExpressionVisitParameter(ParameterExpressionnode){returnnode==_source?_target:base.VisitParameter(node);}}}

Known Issues

Mapping a single type in the source expression to multiple types in the destination expression is not supported e.g.

[Fact]publicvoidCan_map_if_source_type_targets_multiple_destination_types_in_the_same_expression(){varmapper=ConfigurationHelper.GetMapperConfiguration(cfg =>{cfg.CreateMap<SourceType,TargetType>().ReverseMap();cfg.CreateMap<SourceChildType,TargetChildType>().ReverseMap();// Same source type can map to different target types. This seems unsupported currently.cfg.CreateMap<SourceListItemType,TargetListItemType>().ReverseMap();cfg.CreateMap<SourceListItemType,TargetChildListItemType>().ReverseMap();}).CreateMapper();Expression<Func<SourceType,bool>>sourcesWithListItemsExpr= src =>src.Id!=0&&src.ItemList.Any()&&src.Child.ItemList.Any();// Sources with non-empty ItemListExpression<Func<TargetType,bool>>target1sWithListItemsExpr=mapper.MapExpression<Expression<Func<TargetType,bool>>>(sourcesWithListItemsExpr);}privateclassSourceChildType{publicintId{get;set;}publicIEnumerable<SourceListItemType>ItemList{get;set;}// Uses same type (SourceListItemType) for its itemlist as SourceType}privateclassSourceType{publicintId{get;set;}publicSourceChildTypeChild{set;get;}publicIEnumerable<SourceListItemType>ItemList{get;set;}}privateclassSourceListItemType{publicintId{get;set;}}privateclassTargetChildType{publicvirtualintId{get;set;}publicvirtualICollection<TargetChildListItemType>ItemList{get;set;}=[];}privateclassTargetChildListItemType{publicvirtualintId{get;set;}}privateclassTargetType{publicvirtualintId{get;set;}publicvirtualTargetChildTypeChild{get;set;}publicvirtualICollection<TargetListItemType>ItemList{get;set;}=[];}privateclassTargetListItemType{publicvirtualintId{get;set;}}