private InitExpressionResult <Func <T, T, T> > CreateCoalesceWith(
ConstructorInfo constructor)
{
var readableProperties = new List <PropertyInfo>(
from p in typeof(T).GetRuntimeProperties()
where p.CanRead
select p);
var readonlyProperties = new HashSet <PropertyInfo>(
from p in readableProperties
where false == p.CanWrite
select p);
var settableProperties = new HashSet <PropertyInfo>(
from p in readableProperties
where p.CanWrite
select p);
ParameterExpression left = Parameter(typeof(T), nameof(left));
ParameterExpression right = Parameter(typeof(T), nameof(right));
var arguments = new List <Expression>();
foreach (ParameterInfo parameter in constructor.GetParameters())
{
PropertyInfo property =
PickParameterMatch(readonlyProperties, parameter) ??
PickParameterMatch(settableProperties, parameter);
if (property == null)
{
InitExpressionError error =
GetNoPropertyMatchesParameterError(
constructor, parameter);
return(InitExpressionResult <Func <T, T, T> > .WithError(error));
}
arguments.Add(CoalesceOrMemberAccess(property, left, right));
}
if (readonlyProperties.Any())
{
InitExpressionError error =
GetPropertyCannotBeSetError(
constructor, readonlyProperties);
return(InitExpressionResult <Func <T, T, T> > .WithError(error));
}
MemberInitExpression memberInitExpression = MemberInit(
New(constructor, arguments),
from property in settableProperties
select Bind(
property,
CoalesceOrMemberAccess(property, left, right)));
Expression <Func <T, T, T> > lambdaExpression =
Lambda <Func <T, T, T> >(memberInitExpression, left, right);
return(new InitExpressionResult <Func <T, T, T> >(lambdaExpression));
}
private static Func <TModel, TModel, TModel> BuildImplementor()
{
var factory = new InitExpressionFactory <TModel>();
InitExpressionResult <Func <TModel, TModel, TModel> > result =
factory.CreateCoalesce();
return((newValue, lastValue) =>
{
var coalescable = newValue as ICoalescable <TModel>;
if (coalescable != null)
{
return coalescable.Coalesce(lastValue);
}
if (false == result.IsSuccess)
{
var message = string.Join(
Environment.NewLine,
from error in result.Errors
select error.GetExceptionMessage());
throw new InvalidOperationException(message);
}
return result.Function.Invoke(newValue, lastValue);
});
}
public InitExpressionResult <Func <T, T, T> > CreateCoalesce()
{
IEnumerable <ConstructorInfo> constructors =
typeof(T).GetTypeInfo().DeclaredConstructors;
var results = new List <InitExpressionResult <Func <T, T, T> > >(
from constructor in constructors
orderby constructor.GetParameters().Length descending
select CreateCoalesceWith(constructor));
return(results.FirstOrDefault(r => r.IsSuccess)
?? InitExpressionResult <Func <T, T, T> > .WithErrors(
from r in results
from e in r.Errors
select e));
}
