Reflection recursive display of object with attributes types, names and values

I have some complex objects that I would like to print out including the attributes names, types and values. As long as I don't know in advance the amount and depth of all attributes/sub-attributes, I need a recursive call including a loop. I have done it for 2 levels

StringBuilder descr = new StringBuilder();
foreach (PropertyInfo propertyInfo in req.GetType().GetProperties())
{
  if (propertyInfo.CanRead)
  {
    string attributValue = "";
    string attributName = propertyInfo.Name;
    Type attributType = propertyInfo.PropertyType;
    var propertyInfoValue = propertyInfo.GetValue(req, null);

    //if (attributType == typeof(XFkType))
    if (attributType != typeof(System.String) &&
        attributType != typeof(System.Boolean))
    {
        PropertyInfo[] nestedpropertyInfoArray = propertyInfo.PropertyType.GetProperties();
        attributValue += "{";
        foreach (PropertyInfo subProperty in nestedpropertyInfoArray)
        {
            // var instance = (EntityBase)Activator.CreateInstance(subClass);
            attributValue += subProperty.Name + "=";
            try
            {
                attributValue += propertyInfoValue == null ? "" : subProperty.GetValue(propertyInfoValue, null).ToString();
            }
            catch (Exception e)
            {
                attributValue += "null";
            }
            attributValue += ","; 

        }
        attributValue = attributValue.Length > 1 ? attributValue.Substring(0, attributValue.Length - 1) : attributValue;
        attributValue += "}";
    }
    else
        attributValue = propertyInfo.GetValue(req, null) == null ? "" : propertyInfo.GetValue(req, null).ToString();

    descr.Append("[" + propertyInfo.PropertyType + "]" + attributName + "=" + attributValue + " | ");
  }
}

The result is something like:

[XPhone]class{Phone,protocol=SIP,protocolSide=User,callingSearchSpaceName=XFkType,devicePoolName=XFkType,commonDeviceConfigName=XFkType,commonPhoneConfigName=XFkType,networkLocation=Use System Default,locationName=XFkType,mediaResourceListName=null,wirelessLanProfileGroup=null,ctiid=null} | [System.UInt64]sequence={} | [System.Boolean]sequenceSpecified=False |