Headers

As Context Info

Header values can be accessed through the HTTP trigger context.

Binding

Header values can be automatically bound to command properties by adding a header mapping to the function declaration using the AddHeaderMapping method. In the following example the property OperationId will be mapped from the header x-operation-id:

public class FunctionAppConfiguration : IFunctionAppConfiguration
{
    public void Build(IFunctionHostBuilder builder)
    {
        builder
            .Setup((serviceCollection, commandRegistry) =>
            {
                commandRegistry.Register<InvoiceQueryHandler>();
            })
            .Functions(functions => functions
                .HttpRoute("Invoice", route => route
                    .HttpFunction<InvoiceQuery>(HttpMethod.Get)
                        .Options(options => options.AddHeaderMapping(x => x.OperationId, "x-operation-id"))
                )
            );
    }
}

Additionally default mappings can be configured for all commands using the DefaultHttpHeaderBindingConfiguration method as shown below:

public class FunctionAppConfiguration : IFunctionAppConfiguration
{
    public void Build(IFunctionHostBuilder builder)
    {
        builder
            .Setup((serviceCollection, commandRegistry) =>
            {
                commandRegistry.Register<InvoiceQueryHandler>();
            })
            .DefaultHttpHeaderBindingConfiguration(new HeaderBindingConfiguration
            {
                PropertyFromHeaderMappings = new Dictionary<string, string>
                {
                    { "OperationId", "x-operation-id" }
                }
            })
            .Functions(functions => functions
                .HttpRoute("Invoice", route => route
                    .HttpFunction<InvoiceQuery>(HttpMethod.Get)
                )
            );
    }
}

In the case that there are multiple values for a header the first will be used.

Header binding occurs after body, route, and query parameter binding.