Skip to main content

Scalars

Scalar types are the primitives of our schema and can hold a specific type of data. They are leaf types, meaning we cannot use e.g. { fieldName } to further drill down into the type. The main purpose of a scalar is to define how a value is serialized and deserialized.

Besides basic scalars like String and Int, we can also create custom scalars like CreditCardNumber or SocialSecurityNumber. These custom scalars can greatly enhance the expressiveness of our schema and help new developers to get a grasp of our API.

GraphQL scalars​

The GraphQL specification defines the following scalars.

String​

This scalar represents an UTF-8 character sequence. It is automatically inferred from the usage of the .NET string type.

Boolean​

This scalar represents a Boolean value, which can be either true or false. It is automatically inferred from the usage of the .NET bool type.

Int​

This scalar represents a signed 32-bit numeric non-fractional value. It is automatically inferred from the usage of the .NET int type.

Float​

This scalar represents double-precision fractional values, as specified by IEEE 754. It is automatically inferred from the usage of the .NET float or double type.

info

There is a separate Decimal scalar to handle decimal values.

ID​

This scalar is used to facilitate technology-specific Ids, like int, string or Guid. It is not automatically inferred and the IdType needs to be explicitly specified.

ID values are always represented as a String in client-server communication, but can be coerced to their expected type on the server.

public class Product
{
    [GraphQLType(typeof(IdType))]
    public int Id { get; set; }
}

public class Query
{
    public Product GetProduct([GraphQLType(typeof(IdType))] int id)
    {
        // Omitted code for brevity
    }
}

Notice how our code uses int for the Id, but in a request/response it would be serialized as a string. This allows us to switch the CLR type of our Id, without affecting the schema and our clients.