How to assign C# dynamic variable properties to another dynamic object?

Question

I'm trying to write a function which creates an object of Type t and assign its properties.

    internal static object CreateInstanceWithParam(Type t, dynamic d)
    {
        //dynamic obj =  t.GetConstructor(new Type[] { d }).Invoke(new object[] { d });

        dynamic obj =  t.GetConstructor(new Type[] { }).Invoke(new object[] { });
        foreach (var prop in d.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public))
        {
            //prop.Name, 
            //prop.GetValue(d, null);

            // assign the properties and corresponding values to newly created object ???
        }
        return obj;
    }

Then I should be able to use this for any kind of class types like

IUser user = (IUser)CreateInstanceWithParam(userType, new { UserID = 0, Name = "user abc", LoginCode = "abc", DefaultPassword = "xxxxxx" });

IUnit newUnit = (IUnit)CreateInstanceWithParam(unitType, new { ID = 3, Code = "In", Name = "Inch", Points = "72" })

How can I assign the property prop.Name to obj?

Why are you using dynamic at all? If you're doing everything with reflection, I can't see that you're actually doing anything that makes use of it being dynamic. — Jon Skeet
– Jon Skeet, Commented Jun 20, 2013 at 7:22

Jon Skeet · Accepted Answer · 2013-06-20 07:24:57Z

3

Assuming you're just trying to copy properties, you don't need dynamic at all:

internal static object CreateInstanceWithParam(Type type, object source)
{
    object instance = Activator.CreateInstance(type);
    foreach (var sourceProperty in d.GetType()
                                    .GetProperties(BindingFlags.Instance | 
                                                   BindingFlags.Public))
    {
        var targetProperty = type.GetProperty(sourceProperty.Name);
        // TODO: Check that the property is writable, non-static etc
        if (targetProperty != null)
        {
            object value = sourceProperty.GetValue(source);
            targetProperty.SetValue(instance, value);
        }
    }
    return instance;
}

answered Jun 20, 2013 at 7:24

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Sen Jacob Over a year ago

Thanks, I'm not copying properties. Now the values are just hard-coded as given in the question. I'm just trying to decouple two assemblies.

Marc Gravell Over a year ago

@SenJacob maybe investigate automapper?

Jon Skeet Over a year ago

@SenJacob: Well what are you trying to do? If you're going to "assign the property prop.Name to obj" you need to have a value... what value do you want? Your comment says: "assign the properties and corresponding values to newly created object" - in what way is that not copying properties?

Sen Jacob Over a year ago

@JonSkeet Sorry for my bad English.. I meant that I'm not copying properties of another object I already have. the properties and values are given as a dynamic object like new { UserID = 0, Name = "user abc", LoginCode = "abc", DefaultPassword = "xxxxxx" }

Marc Gravell Over a year ago

@SenJacob that is not a "dynamic object"; that is an instance of an anonymous type, which is actually a regular static-typed class; the only interesting things about it are that a: we don't create the class ourselves (the compiler does), and b: we do not know the type-name

|

Marc Gravell · Accepted Answer · 2013-06-20 07:28:19Z

Actually, using dynamic would probably be a bad thing here; the objects you are passing in are instances of anonymous types - no need for dynamic. In particular, dynamic member access is not the same as reflection, and you cannot guarantee that an object described as dynamic will return anything interesting from .GetType().GetProperties(); consider ExpandoObject, etc.

However, FastMember (available on NuGet) may be useful:

internal static object CreateInstanceWithParam(Type type, object template)
{
    TypeAccessor target = TypeAccessor.Create(type),
        source = TypeAccessor.Create(template.GetType());
    if (!target.CreateNewSupported)
            throw new InvalidOperationException("Cannot create new instance");
    if (!source.GetMembersSupported)
            throw new InvalidOperationException("Cannot enumerate members");
    object obj = target.CreateNew();
    foreach (var member in source.GetMembers())
    {
        target[obj, member.Name] = source[template, member.Name];
    }
    return obj;
}

In particular, this can use the dynamic API just as easily as the reflection API, and you never usually see the difference.

Collectives™ on Stack Overflow

How to assign C# dynamic variable properties to another dynamic object?

2 Answers 2

6 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related