LINQ 表达式“无法翻译”

Question

I have migrated my application from dotNet core2.1 to Dotnet core5. The below function has stopped working. I tried to debug the code but I was not able find the solution. The line which is giving error is X => Convert.ToInt32(X.Value) . If I don't do the conversion function works fine but the order of list gets disturbs.

Error :-

The LINQ expression 'DbSet<EbDepartmentMsts>()\\r\\n .OrderBy(e => Convert.ToInt32(e.DeptCode.ToString()))' could not be translated. Additional information: Translation of method 'object.ToString' failed. If this method can be mapped to your custom function, Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'

function

public List<SelectListItem> GetDepartmentCode()
        {
            var table = new List<SelectListItem>();
            try
            {
                table = (from eb in _context.EbDepartmentMsts

                         select new SelectListItem
                         {
                             Text = string.Concat(eb.DeptCode.ToString(), "~", eb.Description),
                             Value = eb.DeptCode.ToString()
                         }).OrderBy(X => Convert.ToInt32(X.Value)).ToList();

            }catch(Exception ex)
            {

            }
            return table;
        }

Answer 1

You need to materialize the LINQ query via .ToList() , then perform .Select() .

From the existing LINQ query,

select eb.DeptCode, eb.Description

for querying only required fields.

table = (from eb in _context.EbDepartmentMsts
         select new { eb.DeptCode, eb.Description }
        )
        .ToList()
        .Select(x => new SelectListItem
        {
            Text = string.Concat(x.DeptCode.ToString(), "~", x.Description),
            Value = x.DeptCode.ToString()
        })
        .OrderBy(x => Convert.ToInt32(x.Value))
        .ToList();