c# - How to iterate through classes fields and set properties

Here's a complete working example:

public class Person
{
    public string Name { get; set; }
}

class Program
{
    static void PropertySet(object p, string propName, object value)
    {
        Type t = p.GetType();
        PropertyInfo info = t.GetProperty(propName);
        if (info == null)
            return;
        if (!info.CanWrite)
            return;
        info.SetValue(p, value, null);
    }

    static void PropertySetLooping(object p, string propName, object value)
    {
        Type t = p.GetType();
        foreach (PropertyInfo info in t.GetProperties())
        {
            if (info.Name == propName && info.CanWrite)
            {
                info.SetValue(p, value, null);
            }
        }
    }

    static void Main(string[] args)
    {
        Person p = new Person();

        PropertySet(p, "Name", "Michael Ellis");
        Console.WriteLine(p.Name);
        PropertySetLooping(p, "Name", "Nigel Mellish");
        Console.WriteLine(p.Name);
    }
}

EDIT: added a looping variant so you could see how to loop through property info objects.

public class Person
{
    public string Name { get; set; }
}

public class Employee
{
    public Person person = new Person();

    public void DynamicallySetPersonProperty()
    {
        var p = GetType().GetField("person").GetValue(this);
        p.GetType().GetProperty("Name").SetValue(p, "new name", null);
    }
}

With the following Extension methods that I have created, you can set or get any property value even if they are nested

GetPropertyValue(customObject, "Property.Nested.Child.Name");

or set

SetPropertyValue(customObject, "Property.Nested.Child.Name", "my custom name");

        private class TargetProperty
    {
        public object Target { get; set; }
        public PropertyInfo Property { get; set; }

        public bool IsValid { get { return Target != null && Property != null; } }
    }

    private static TargetProperty GetTargetProperty(object source, string propertyName)
    {
        if (!propertyName.Contains("."))
            return new TargetProperty { Target = source, Property = source.GetType().GetProperty(propertyName) };

        string[] propertyPath = propertyName.Split('.');

        var targetProperty = new TargetProperty();

        targetProperty.Target = source;
        targetProperty.Property = source.GetType().GetProperty(propertyPath[0]);

        for (int propertyIndex = 1; propertyIndex < propertyPath.Length; propertyIndex++)
        {
            propertyName = propertyPath[propertyIndex];
            if (!string.IsNullOrEmpty(propertyName))
            {
                targetProperty.Target = targetProperty.Property.GetValue(targetProperty.Target, null);
                targetProperty.Property = targetProperty.Target.GetType().GetProperty(propertyName);
            }
        }

        return targetProperty;
    }


    public static bool HasProperty(this object source, string propertyName)
    {
        return GetTargetProperty(source, propertyName).Property != null;
    }

    public static object GetPropertyValue(this object source, string propertyName)
    {
        var targetProperty = GetTargetProperty(source, propertyName);
        if (targetProperty.IsValid)
        {
            return targetProperty.Property.GetValue(targetProperty.Target, null);
        }
        return null;
    }

    public static void SetPropertyValue(this object source, string propertyName, object value)
    {
        var targetProperty = GetTargetProperty(source, propertyName);
        if(targetProperty.IsValid)
        {
            targetProperty.Property.SetValue(targetProperty.Target, value, null);
        }
    }

And here are a couple of tests for it

    [TestFixture]
public class ObjectExtensionsTest
{

    private class MockClass
    {
        public MockClass()
        {
            Nested = new NestedMockClass();
        }

        public string Id { get; set; }
        public string Name { get; set; }

        public string GetOnly { get { return "MockClass"; } }
        public string SetOnly { set { } }

        public NestedMockClass Nested { get; set; }
    }

    private class NestedMockClass
    {
        public string NestedId { get; set; }
        public string NestedName { get; set; }

        public string NestedGetOnly { get { return "NestedMockClass"; } }
        public string NestedSetOnly { set { } }
    }

    [Test]
    public void TestShouldFindProperty()
    {
        MockClass mockObject = new MockClass();

        Assert.IsTrue(mockObject.HasProperty("Id"));
        Assert.IsTrue(mockObject.HasProperty("Name"));
        Assert.IsTrue(mockObject.HasProperty("GetOnly"));
        Assert.IsTrue(mockObject.HasProperty("SetOnly"));
        Assert.IsTrue(mockObject.HasProperty("Nested"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedId"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedName"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedGetOnly"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedSetOnly"));
    }

    [Test]
    public void TestShouldGetPropertyValue()
    {
        MockClass mockObject = new MockClass();

        mockObject.Id = "1";
        mockObject.Name = "Name";
        mockObject.Nested.NestedId = "NestedId";
        mockObject.Nested.NestedName = "NestedName";

        Assert.AreEqual(mockObject.Id, mockObject.GetPropertyValue("Id"));
        Assert.AreEqual(mockObject.Name, mockObject.GetPropertyValue("Name"));
        Assert.AreEqual(mockObject.GetOnly, mockObject.GetPropertyValue("GetOnly"));
        Assert.AreEqual(mockObject.Nested.NestedId, mockObject.GetPropertyValue("Nested.NestedId"));
        Assert.AreEqual(mockObject.Nested.NestedName, mockObject.GetPropertyValue("Nested.NestedName"));

    }

    [Test]
    public void TestShouldSetPropertyValue()
    {
        MockClass mockObject = new MockClass();

        mockObject.SetPropertyValue("Id", "1");
        mockObject.SetPropertyValue("Name", "Name");
        mockObject.SetPropertyValue("Nested.NestedId", "NestedId");
        mockObject.SetPropertyValue("Nested.NestedName", "NestedName");

        Assert.AreEqual(mockObject.Id, "1");
        Assert.AreEqual(mockObject.Name, "Name");
        Assert.AreEqual(mockObject.Nested.NestedId, "NestedId");
        Assert.AreEqual(mockObject.Nested.NestedName, "NestedName");

    }
}

Hope you find it useful.

You are trying to set the Name property of your Employee class's _person field. It doesn't have one. Try this:

prop.SetValue(((FieldInfo)member).GetValue(this), "new name", null)

Not sure if you need to cast the first argument like this:

prop.SetValue((Person)((FieldInfo)member).GetValue(this), "new name", null)

This then applies it to the value of the _person field instead.