GraphQL.EntityFrameworkCore.Helpers 0.2.5

GraphQL Helpers for EF Core - Connections, Selection from Request and More

Helpers to add bidirectional cursor based paginaton to your endpoints with the IQueryable extension method ToConnection. The method expects a request that implements IConnectionInput<T> as input. Parameters is added to the ConnectionBuilder using the extension method Paged(defaultPageSize).

The Select(IResolveFieldContext context) extension methods helps you to avoid overfetching data by only selecting the fields requested. Foreign key fields are included by default as the value might be used for data loaded fields (requires DbContext.IModel). ToConnection is using this method per default.

With the Filter(context) extension method you can filter a list of items based on a search string. What columns should be filterable is determined by the FilterableAttribute. The filter parameter is applied Filterable extension.

Getting Started

dotnet add package GraphQL.EntityFrameworkCore.Helpers

Examples

Connection

Bidirectional cursor based pagination with support for ordering, filtering and selecting based on what is requested.

With the parameter orderBy (array of strings, i.e [ "name", "id" ]) you can specify in the client what order you want the items in. The order will be ascending by default, you can change it to descending by setting the parameter isAsc to false.

It is important that each resulting cursor points at a unique row in order to be able to determine what rows to include before or after a specific row. Therefore the primary key(s) of a certain entity is automaticaly included in the orderBy if the asked for order by columns isn't considered unique. Columns considered unique is either the primary key, has a unique constraint or is of type GUID, DATETIME or DATETIMEOFFSET. If you have column that you know are unique but doesn't meet those criterias you can use the Unique attribute.

Connection<DroidGraphType>()
    .Name("Droids")
    .Paged()
    .ResolveAsync(async context =>
    {
        var request = new ConnectionInput();
        request.SetConnectionInput(context);

        return await dbContext.Droids
            .ToConnection(request, dbContext.Model); // IModel is required for Select from Request
    });

Validating the request

You can validate the request outside of ToConnection if you want to ensure it's valid in your validation pipeline, the first generic type parameter is the DbSet and the second parameter is the resulting type of the request. It needs the IModel to determine that the orderBy is valid, it doesn't need a orderBy if there is primary key it could use instead.

var validationResult = request.Validate<Human, Clone>(dbContext.Model);

Select from Request

FieldAsync<ListGraphType<HumanGraphType>>(
    "Humans",
    resolve: async context => await dbContext.Humans.Select(context, dbContext.Model).ToListAsync());

Filter

Add FilterableAttribute columns that should be filterable.

public class Human
{
    public Guid Id { get; set; }

    [Filterable]
    public string Name { get; set; }
}

Add the argument to the FieldBuilder using the extension method Filterable() and filter the list with the IQueryable extension method Filter(context).

Field<ListGraphType<HumanGraphType>>()
    .Name("Humans")
    .Filterable()
    .ResolveAsync(async context => await dbContext.Humans
        .Filter(context)
        .Select(context, dbContext.Model)
        .ToListAsync());