CODEWITHSUNDEEP
c#.netreflection
NewDTinStackoverflow
NewDTinStackoverflow

Reputation: 543

loop through an object and find the not null properties

I have 2 instances of the same objects, o1, and o2. If I am doing things like

 if (o1.property1 != null) o1.property1 = o2.property1

for all the properties in the object. What would be the most efficient way to loop through all properties in an Object and do that? I saw people using PropertyInfo to check nulll of the properties but it seems like they could only get through the PropertyInfo collection but not link the operation of the properties.

Thanks.

Upvotes: 7

Views: 6672

Answers (3)

dotarj
dotarj

Reputation: 488

If you are going to use this many times, you could use a compiled expression for better performance:

public static class Mapper<T>
{
    static Mapper()
    {
        var from = Expression.Parameter(typeof(T), "from");
        var to = Expression.Parameter(typeof(T), "to");

        var setExpressions = typeof(T)
            .GetProperties()
            .Where(property => property.CanRead && property.CanWrite && !property.GetIndexParameters().Any())
            .Select(property =>
            {
                var getExpression = Expression.Call(from, property.GetGetMethod());
                var setExpression = Expression.Call(to, property.GetSetMethod(), getExpression);
                var equalExpression = Expression.Equal(Expression.Convert(getExpression, typeof(object)), Expression.Constant(null));

                return Expression.IfThen(Expression.Not(equalExpression), setExpression);
            });

        Map = Expression.Lambda<Action<T, T>>(Expression.Block(setExpressions), from, to).Compile();
    }

    public static Action<T, T> Map { get; private set; }
}

And use it like this:

Mapper<Entity>.Map(e1, e2);

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1499890

You can do this with reflection:

public void CopyNonNullProperties(object source, object target)
{
    // You could potentially relax this, e.g. making sure that the
    // target was a subtype of the source.
    if (source.GetType() != target.GetType())
    {
        throw new ArgumentException("Objects must be of the same type");
    }

    foreach (var prop in source.GetType()
                               .GetProperties(BindingFlags.Instance |
                                              BindingFlags.Public)
                               .Where(p => !p.GetIndexParameters().Any())
                               .Where(p => p.CanRead && p.CanWrite))
    {
        var value = prop.GetValue(source, null);
        if (value != null)
        {
            prop.SetValue(target, value, null);
        }
    }
}

Upvotes: 14

Jan-Peter Vos
Jan-Peter Vos

Reputation: 3197

Judging from your example i think your looking for something like this:

static void CopyTo<T>(T from, T to)
{
    foreach (PropertyInfo property in typeof(T).GetProperties())
    {
        if (!property.CanRead || !property.CanWrite || (property.GetIndexParameters().Length > 0))
            continue;

        object value = property.GetValue(to, null);
        if (value != null)
            property.SetValue(to, property.GetValue(from, null), null);
    }
}

Upvotes: 2

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