How to Correctly Use Dapper's `splitOn` Parameter in Multimapping?

Correctly Utilizing Multimapping in Dapper

Dapper's multimapping feature is a powerful tool for mapping complex data structures from SQL queries. However, proper usage of this feature is crucial to avoid issues.

In the provided code, the splitOn parameter should only specify the column(s) where the mapped objects split. By default, Dapper assumes "Id" as the split point. To specify multiple split points for different objects, they should be provided as a comma-delimited list.

For example, in the given scenario:

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

The splitOn parameter correctly specifies "CustomerId" as the split point between the ProductItem and Customer objects. Therefore, omitting "CustomerName" from the splitOn list would not result in a null customer name, as the code provided in the answer implies.

It's important to note that the order of columns in the SQL result set should match the order specified in the splitOn parameter to ensure correct mapping. If the column ordering changes, the splitOn parameter must be adjusted accordingly.

The above is the detailed content of How to Correctly Use Dapper's `splitOn` Parameter in Multimapping?. For more information, please follow other related articles on the PHP Chinese website!