public object CreateInstance(IServiceProvider provider)
{
for (var index = 0; index != _parameters.Length; index++)
{
if (_parameterValuesSet[index] == false)
{
var value = provider.GetService(_parameters[index].ParameterType);
if (value == null)
{
if (!ParameterDefaultValue.TryGetDefaultValue(_parameters[index], out var defaultValue))
{
throw new InvalidOperationException(
$"Unable to resolve service for type '{_parameters[index].ParameterType}' while attempting to activate '{_constructor.DeclaringType}'.");
}
_parameterValues[index] = defaultValue;
}
else
{
_parameterValues[index] = value;
}
}
}
return(_constructor.Invoke(BindingFlags.DoNotWrapExceptions, null, _parameterValues, null));
}
private static Expression BuildFactoryExpression(
ConstructorInfo constructor,
int?[] parameterMap,
Expression serviceProvider,
Expression factoryArgumentArray)
{
var constructorParameters = constructor.GetParameters();
var constructorArguments = new Expression[constructorParameters.Length];
for (var i = 0; i < constructorParameters.Length; i++)
{
var constructorParameter = constructorParameters[i];
var parameterType = constructorParameter.ParameterType;
var hasDefaultValue = ParameterDefaultValue.TryGetDefaultValue(constructorParameter, out var defaultValue);
if (parameterMap[i] != null)
{
constructorArguments[i] = Expression.ArrayAccess(factoryArgumentArray, Expression.Constant(parameterMap[i]));
}
else
{
var parameterTypeExpression = new[]
{
serviceProvider,
Expression.Constant(parameterType, typeof(Type)),
Expression.Constant(constructor.DeclaringType, typeof(Type)),
Expression.Constant(hasDefaultValue)
};
constructorArguments[i] = Expression.Call(GetServiceInfo, parameterTypeExpression);
}
// Support optional constructor arguments by passing in the default value
// when the argument would otherwise be null.
if (hasDefaultValue)
{
var defaultValueExpression = Expression.Constant(defaultValue);
constructorArguments[i] = Expression.Coalesce(constructorArguments[i], defaultValueExpression);
}
constructorArguments[i] = Expression.Convert(constructorArguments[i], parameterType);
}
return(Expression.New(constructor, constructorArguments));
}
public object CreateInstance(IServiceProvider provider)
{
for (var index = 0; index != _parameters.Length; index++)
{
if (_parameterValuesSet[index] == false)
{
var value = provider.GetService(_parameters[index].ParameterType);
if (value == null)
{
if (!ParameterDefaultValue.TryGetDefaultValue(_parameters[index], out var defaultValue))
{
throw new InvalidOperationException(
$"Unable to resolve service for type '{_parameters[index].ParameterType}' while attempting to activate '{_constructor.DeclaringType}'.");
}
_parameterValues[index] = defaultValue;
}
else
{
_parameterValues[index] = value;
}
}
}
#if NETCOREAPP3_1
return(_constructor.Invoke(BindingFlags.DoNotWrapExceptions, binder: null, parameters: _parameterValues, culture: null));
#else
try
{
return(_constructor.Invoke(_parameterValues));
}
catch (TargetInvocationException ex) when(ex.InnerException != null)
{
ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
// The above line will always throw, but the compiler requires we throw explicitly.
throw;
}
#endif
}