Configuration Value

ConfigurationExpression reads a typed value from IConfiguration within an expression tree. It is the expression tree equivalent of IConfiguration.GetValue<T>("key").

Like InjectExpression, the configuration source is injected at compile time via lambda.Compile(serviceProvider), which resolves IConfiguration from the container and binds it to all ConfigurationExpression nodes before compilation.

Factory Methods

using static Hyperbee.Expressions.ExpressionExtensions;

Overload	Description
`ConfigurationValue( Type type, string key )`	Typed read – provider supplied at compile time
`ConfigurationValue( Type type, IConfiguration config, string key )`	Typed read with explicit configuration
`ConfigurationValue<T>( string key )`	Generic read – provider supplied at compile time
`ConfigurationValue<T>( IConfiguration config, string key )`	Generic read with explicit configuration

Usage

Read a Value at Compile Time

using static System.Linq.Expressions.Expression;
using static Hyperbee.Expressions.ExpressionExtensions;

// Build the tree (IConfiguration resolved later from DI)
var timeout = ConfigurationValue<int>( "App:TimeoutMs" );

var expr = Block(
    Call(
        typeof(Console).GetMethod("WriteLine", [typeof(int)])!,
        timeout
    )
);

var lambda = Lambda<Action>( expr );

// serviceProvider must have IConfiguration registered
var fn = lambda.Compile( serviceProvider );
fn();   // prints the value of App:TimeoutMs

With an Explicit IConfiguration

IConfiguration config = new ConfigurationBuilder()
    .AddInMemoryCollection( new Dictionary<string, string?> { ["Name"] = "Hyperbee" } )
    .Build();

var name = ConfigurationValue<string>( config, "Name" );

var lambda = Lambda<Func<string>>( name );
var fn = lambda.Compile();
Console.WriteLine( fn() );  // "Hyperbee"

Read Multiple Keys

var host = ConfigurationValue<string>( "Database:Host" );
var port = ConfigurationValue<int>( "Database:Port" );

var expr = Block(
    StringFormat( Constant( "{0}:{1}" ), [host, port] )
);

Notes

ConfigurationExpression implements IDependencyInjectionExpression. The Compile(serviceProvider) extension resolves IConfiguration from the container and sets it on every ConfigurationExpression in the tree.
If no configuration is available and the key is missing, the value defaults to the type’s default (null for reference types, 0 for numeric types).
See Inject for service resolution.
See Dependency Injection for the full DI pattern.