//https://stackoverflow.com/a/39617419/4682355
public static Expression CreateNullPropagationExpression(Expression o, Expression call, MemberInfo memberInfo)
{
Expression propertyAccess = call;
var propertyType = TypeHelper.GetMemberType(memberInfo);
if (propertyType.IsValueType && !TypeHelper.IsNullable(propertyType))
{
return(propertyAccess);
}
var nullResult = Expression.Default(propertyAccess.Type);
var condition = Expression.Equal(o, Expression.Constant(null, o.Type));
return(Expression.Condition(condition, nullResult, propertyAccess));
}
public static Action <T, V> GetExpressionSet(string name, List <MemberParseInfo> list)
{
var last = list.Last();
var first = list.First();
var target = Expression.Parameter(typeof(T), "target");
var value = Expression.Parameter(typeof(V), "value");
var returnLabel = Expression.Label();
var locals = new ParameterExpression[list.Count - 1];
var labels = new LabelTarget[list.Count];
List <Expression> body = new List <Expression>();
for (int i = 0; i < list.Count - 1; i++)
{
var info = list[i];
locals[i] = Expression.Variable(TypeHelper.GetMemberType(info.Info), info.Info.Name.ToLower());
}
for (int i = 0; i < list.Count; i++)
{
labels[i] = Expression.Label();
}
int j = 0;
for (int i = 0; i < list.Count; i++)
{
var info = list[i];
var type = TypeHelper.GetMemberType(info.Info);
if (i < list.Count - 1)
{
var call = Call(i == 0 ? target : locals[i - 1], info, i);
body.Add(Expression.Assign(locals[i], call));
if (!type.IsValueType || TypeHelper.IsNullable(type))
{
body.Add(Expression.IfThenElse(Expression.Equal(locals[i], Expression.Constant(null, type)),
Expression.Return(returnLabel),
Expression.Label(labels[j++])));
}
}
else
{
for (int r = list.Count - 1; r >= 0; r--)
{
info = list[r];
type = TypeHelper.GetMemberType(info.Info);
if (type.IsValueType || r == list.Count - 1)
{
var param = r == 0 ? target : locals[r - 1];
var setValue = r == list.Count - 1 ? value : locals[r];
if (TypeHelper.CanWrite(info.Info))
{
var call = Call(param, info, r);
body.Add(Expression.Assign(call, setValue));
}
else
{
return(null);
}
}
}
}
}
if (j > 0)
{
body.Add(Expression.Label(returnLabel));
}
return(Expression.Lambda <Action <T, V> >(Expression.Block(locals, body), target, value).Compile());
}