CODEWITHSUNDEEP
.netentity-frameworklinq
Rash
Rash

Reputation: 330

The best overloaded method match for 'System.Collections.Generic.List<XXX.Models.Domain>.Add(XXX.Models.Domain)' has some invalid arguments

I am trying to first search the domain ids from a particular table based on tenant and then for the domain id I am looking for domain names in another table and adding in a list. I am getting an error on adding the domain object in my list. My code is as shown below:

public IEnumerable<Domain> GetAllByTenant(Guid tenantId)
    {
        List<Domain> domains = null;
        var ids = _applicationDbContext.TenantDomainMap.Where(x => x.TenantId == tenantId).Select(x => x.DomainId);

        foreach (var id in ids)
        {
            var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id);
            domains.Add(domain);

        }
        return domains;
    }

I am getting following errors at domains.Add(domain): 1. The best overloaded method match for 'System.Collections.Generic.List.Add(XXX.Models.Domain)' has some invalid arguments 2. cannot convert from 'System.Linq.IQueryable' to 'XXX.Models.Domain'

Please help me in resolving this issue.

Upvotes: 1

Views: 1855

Answers (2)

user1618236
user1618236

Reputation:

The Where method always returns an IQueryable because it has no way of knowing how many items matched your predicate.

There are 4 potential methods you can add after the Where call to resolve this problem.

Single: This method expects only one match and it will throw an exception if more than one match was found or if no matches were found.

 var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id).Single();

SingleOrDefault: This method is the same as Single except that it will return the results of default(T), where T is your type, when no results are found; this is usually null.

 var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id).SingleOrDefault();

First: This method will return the first item in the list and will only throw an exception if no matches were found.

 var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id).First();

FirstOrDefault: This method unlike First will not throw an exception on no matches, instead it works just like SingleOrDefault and will return the type's default value.

 var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id).FirstOrDefault();

Given that you are doing a search on an Id, Single is probably the correct choice, though depending on your saving logic SingleOrDefault may be needed.

Upvotes: 3

JsonStatham
JsonStatham

Reputation: 10374

Try adding a .FirstOrDefault(); to ensure only return the first match returned from the Where.

foreach (var id in ids)
{
      var domain = _applicationDbContext.Domain.Where(x => x.DomainId == id).FirstOrDefault();
      domains.Add(domain);   
}

Where returns type IEnumerable and you need to add a single Domain type to your list, for each.

Upvotes: 1

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