使用select将Entity Framework实体映射到dto对象

Question

I am using Entity Framework and I am trying to map using entities to a dto object using the following code but something is going wrong:

var fileUploads = _dbContext.FileUploads.Include("DocumentType").Include("Store");

if (jobSearchParams.DocumentTypeId != null)
{
    fileUploads = fileUploads.Where(x => x.DocumentTypeID == 6);
}

if (jobSearchParams.StoreId != null)
{
    fileUploads = fileUploads.Where(x => x.StoreID == jobSearchParams.StoreId);
}

if (!string.IsNullOrEmpty(jobSearchParams.Name))
{
    fileUploads = fileUploads.Where(d => d.Name.Contains(jobSearchParams.Name));
}

var dtos = Mapper.Map<IEnumerable<JobDocumentDto>>(documents);

var cnt = fileUploads.Count(); // 1412

var fileDocuments = fileUploads.AsEnumerable().Select(d => new JobDocumentDto
{
    DocumentID = d.ID,
    StoreID = d.StoreID,
    StoreName = d.Store.Name,
    Document = Mapper.Map<DocumentDto>(d),
    DocumentName = d.Name
}).ToList();

cnt  = fileDocuments.Count; // 0

With the AsEnumerable in the expression I have 0 objects after doing the select and if I remove the AsEnumerable I get the following error:

System.NotSupportedException: LINQ to Entities does not recognize the method 'DataManagement.DTOs.DocumentDto MapDocumentDto' method, and this method cannot be translated into a store expression

Answer 1

Add .ToList() before Select, so make it .ToList().Select(...)... .

Reason: LINQ is trying to convert the entire new JobDocumentDto {...} statement into query form, but it can't. By running the query earlier this problem is avoided.

Also the AsEnumerable() may now be redundant, just try removing it.