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));
}
public static InitExpressionResult <TDelegate> WithError(
InitExpressionError error)
{
if (error == null)
{
throw new ArgumentNullException(nameof(error));
}
return(new InitExpressionResult <TDelegate>(new[] { error }));
}