How Can I Correctly Use Dapper's Multimapping to Retrieve All Customer Properties?

Proper Multimapping Usage in Dapper

Multimapping is a feature in Dapper that allows returning multiple object types from a single query. To use it, provide a mapping function that assigns the data to the corresponding objects.

In your example, you're trying to map ProductItems and Customers from the query:

var sql = @"select * from Product p
            inner join Customer c on p.CustomerId = c.CustomerId 
            order by p.ProductName";

var data = con.Query<ProductItem, Customer, ProductItem>(
    sql,
    (productItem, customer) => {
        productItem.Customer = customer;
        return productItem;
    },
    splitOn: &quot;CustomerId,CustomerName&quot;
);

However, you're experiencing issues with returning all customer properties. This is because the splitOn parameter indicates the columns that separate two objects. If you don't specify CustomerName, Dapper assumes it's at the end of the result set and assigns it null.

To solve this, ensure that CustomerId is specified first in splitOn and CustomerName is second. This will split the result set correctly. However, if the Column ordering in the table changes, this can result in null customer names.

Note: If the result set has multiple split points, list them in a comma-delimited format. Dapper will split the result set into multiple objects based on these points.

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