GetPropertyValue<T>

public static T GetPropertyValue<T>(this DynamicEntity entity, string propertyName)
{
    // Retrieve the matching property.
    object theProperty = entity.Properties.FirstOrDefault(i => i.Name.EqualsIgnoreCase(propertyName));

    // If property not found, return the default value.
    if (theProperty == null) return default(T);

    object value = null;
    string strPropertyType = theProperty.GetType().Name;

    switch (strPropertyType)
    {
        case "KeyProperty":
            value = ((KeyProperty)theProperty).Value.Value;
            break;

        case "StringProperty":
            value = ((StringProperty)theProperty).Value;
            break;

        case "PicklistProperty":
            if (typeof(T).Equals(typeof(string)))
                value = ((PicklistProperty)theProperty).Value.name;
            else if (typeof(T).Equals(typeof(int)))
                value = ((PicklistProperty)theProperty).Value.Value;

            break;

        case "CrmBooleanProperty":
            value = ((CrmBooleanProperty)theProperty).Value.Value;
            break;

        case "CrmDateTimeProperty":
            value = ((CrmDateTimeProperty)theProperty).Value.Value;
            break;

        case "CrmDecimalProperty":
            value = ((CrmDecimalProperty)theProperty).Value.Value;
            break;

        case "CrmFloatProperty":
            value = ((CrmFloatProperty)theProperty).Value.Value;
            break;

        case "CrmMoneyProperty":
            value = ((CrmMoneyProperty)theProperty).Value.Value;
            break;

        case "CrmNumberProperty":
            value = ((CrmNumberProperty)theProperty).Value.Value;
            break;

        case "LookupProperty":
            if (typeof(T).Equals(typeof(string)))
                value = ((LookupProperty)theProperty).Value.name;
            else if (typeof(T).Equals(typeof(Guid)))
                value = ((LookupProperty)theProperty).Value.Value;

            break;

        case "CustomerProperty":
            if (typeof(T).Equals(typeof(string)))
                value = ((CustomerProperty)theProperty).Value.name;
            else if (typeof(T).Equals(typeof(Guid)))
                value = ((CustomerProperty)theProperty).Value.Value;

            break;

        case "StatusProperty":
            if (typeof(T).Equals(typeof(string)))
                value = ((StatusProperty)theProperty).Value.name;
            else if (typeof(T).Equals(typeof(Guid)))
                value = ((StatusProperty)theProperty).Value.Value;

            break;

        case "StateProperty":
            value = ((StateProperty)theProperty).Value;
            break;

        case "EntityNameReferenceProperty":
            value = ((EntityNameReferenceProperty)theProperty).Value.Value;
            break;
    }

    try
    {
        if (value != null)
        {
            return (T)value;
        }
    }
    catch
    { }

    return default(T);
}

var dynamicContact = ...;
dynamicContact.GetPropertyValue<string>("firstname");

// Will retrieve the user id that modified this record last.
dynamicContact.GetPropertyValue<Guid>("modifiedby");

// Will retrieve the username that modified this record last.
dynamicContact.GetPropertyValue<string>("modifiedby");