---
title: "Why does my Dapper multi-mapping leave the parent object null?"  
description: "Why does my Dapper multi-mapping leave the parent object null?"  
author: "Austin Dcruz"  
published: 2026-09-30  
updated: 2026-09-30  
canonical: https://www.mindstick.com/forum/162230/why-does-my-dapper-multi-mapping-leave-the-parent-object-null  
category: "Data Access"  
tags: ["Dapper", "orm", "Data Mapping", "c#"]  
reading_time: 1 minute  

---

# Why does my Dapper multi-mapping leave the parent object null?

I'm trying to pull back a list of `Order` records where each one carries a nested `Customer` object. I'm using Dapper's `Query<Order, Customer, Order>` overload, but no matter what I do, the `Customer` properties stay `null` after materialization.

Here's the mapper I've been using:

```cs
// Mapper attempt
private Order MapOrder(Order order, Customer customer)
{
    order.Customer = customer; // Never sticks
    return order;
}
```

I've double-checked the `splitOn` column against my `SELECT` list and it lines up. The query itself returns rows fine in SSMS. Is there a registration step I'm missing, or does the overload signature need to change? I'd appreciate any patterns that keep the parent populated without bloating the result set.


---

Original Source: https://www.mindstick.com/forum/162230/why-does-my-dapper-multi-mapping-leave-the-parent-object-null

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