/// <summary>
/// Builds an expression for the given <paramref name="target"/>.
/// </summary>
/// <param name="target">The target whose expression is to be built.</param>
/// <param name="context">The compilation context.</param>
/// <param name="compiler">The expression compiler to be used to build any other expressions for targets
/// which might be required by the <paramref name="target" />. Note that unlike on the interface, where this
/// parameter is optional, this will always be provided</param>
protected override Expression Build(SingletonTarget target, IExpressionCompileContext context, IExpressionCompiler compiler)
{
var holder = context.ResolveContext.Resolve <SingletonTarget.SingletonContainer>();
int? targetIdOverride = context.GetOption <TargetIdentityOverride>(context.TargetType ?? target.DeclaredType);
TypeAndTargetId id = new TypeAndTargetId(context.TargetType ?? target.DeclaredType, targetIdOverride ?? target.Id);
var lazy = holder.GetLazy(id);
if (lazy == null)
{
lazy = holder.GetLazy(
target,
id,
compiler.CompileTargetStrong(
target.InnerTarget,
context.NewContext(
context.TargetType ?? target.DeclaredType,
// this override is important - when forcing into the root-scope, as we do
// for singletons, 'explicit' means absolutely nothing. So, instead of allowing
// our child target to choose, we explicitly ensure that all instances are implicitly
// tracked within the root scope, if it is one which can track instances.
scopeBehaviourOverride: ScopeBehaviour.Implicit,
scopePreferenceOverride: ScopePreference.Root)),
context);
}
return(Expression.Call(
Expression.Constant(lazy),
lazy.GetType().GetMethod("Resolve"),
context.ResolveContextParameterExpression));
}
public object GetLazy(SingletonTarget target, TypeAndTargetId id, Delegate factory, ICompileContext context)
{
return(_lazies.GetOrAdd(id, tid =>
{
return Activator.CreateInstance(
typeof(Entry <>).MakeGenericType(tid.Type),
context.ResolveContext.ChangeRequestedType(tid.Type),
factory);
}));
}
public object GetLazy(TypeAndTargetId id)
{
_lazies.TryGetValue(id, out var result);
return(result);
}
