cannot implicitly convert System.LINQ an explicit conversion exists are you missing a cast

Question

I am currently trying to implement TypeAhead plugin with an API search query. The below code is a snippit I recieved from a udemy class Mosh (https://github.com/mosh-hamedani/vidly-mvc-5/blob/master/Vidly/Controllers/Api/CustomersController.cs). Upon implementing the below code I am receiving the error of

Cannot implicitly convert type 'System.Linq.Iqueryable' to System.Data.Entity.DbSet'. An Explicit conversion exists (are you missing a cast)?

This happens on this line of code

vmrsQuery = vmrsQuery.Where(c => c.Description.Contains(query));

Does anyone else have a workaround to get this to function correctly?

public IHttpActionResult GetVMRS(string query = null)
    {

        var vmrsQuery = _context.VMRS;

        if (!String.IsNullOrWhiteSpace(query))
            vmrsQuery = vmrsQuery.ToList().Where(c => c.Description.Contains(query));

        var vmrsDtos = vmrsQuery
            .ToList()
            .Select(Mapper.Map<VMRS, VMRSDto>);

        return Ok(vmrsDtos);
    }

Answer 1

You shouldn't call ToList() on your context directly. This will pull every row from the database into memory before executing the where clause.

vmrsQuery = vmrsQuery.ToList().Where(c => c.Description.Contains(query));

should be

vmrsQuery = vmrsQuery.Where(c => c.Description.Contains(query));

Also, you probably need to explicitly define your variable.

var vmrsQuery = _context.VMRS;

should be

IQueryable<VMRS> vmrsQuery = _context.VMRS;

This is because the context could be a DbSet if using Entity Framework.

You could also just put _context.VMRS.AsQueryable()