Classes · 2 min read

QueryMultipleExtractor

A class that is being used to extract the information of the multiple resultsets returned by the ExecuteQueryMultiple operation.

The result object of the ExecuteQueryMultiple operation. It provides fine-grained control over how results are extracted from the underlying DbDataReader.

Internally, it wraps the DbDataReader, IDbConnection, and the IDbTransaction (if present), and advances the reader pointer by calling DbDataReader.NextResult() on each extraction call.

Methods

Name	Description
Extract	Extracts the current resultset into a typed object.
Scalar	Returns the first column of the current resultset.

Scalar() accepts a generic type argument. Each call to either method advances the reader to the next resultset.

Usability

Assign the result of ExecuteQueryMultiple to a variable and extract results using the Extract() method.

using (var connection = new SqlConnection(connectionString))
{
    var commandText = "SELECT Id, Name FROM [dbo].[Customer] WHERE Id = @CustomerId; SELECT * FROM [dbo].[Order] WHERE CustomerId = @CustomerId;";

    // Ensure to wrap with 'using' to auto-dispose
    using (var extractor = connection.ExecuteQueryMultiple(commandText, new { CustomerId = 10045 }))
    {
        // We know that the first query is for 'Customer' and second query is for 'Order'
        var customer = extractor.Extract<Customer>().FirstOrDefault();
        var orders = extractor.Extract<Order>().AsList();

        // Do the stuffs for the 'customer' and 'orders' here
    }
}

Or using Scalar().

using (var connection = new SqlConnection(connectionString))
{
    var commandText = "SELECT COUNT(*) FROM [dbo].[Customer]; SELECT GETUTCDATE();";

    // Ensure to wrap with 'using' to auto-dispose
    using (var extractor = connection.ExecuteQueryMultiple(commandText, new { CustomerId = 10045 }))
    {
        // We know that the first query is type 'int' and second query is type 'DateTime'
        var customerCount = extractor.Scalar<int>()
        var serverDate = extractor.Scalar<DateTime>();

        // Do the stuffs for the 'customerCount' and 'serverDate' here
    }
}

Or a combination of both.

using (var connection = new SqlConnection(connectionString))
{
    var commandText = "SELECT Id, Name FROM [dbo].[Customer] WHERE Id = @CustomerId; SELECT COUNT(*) FROM [dbo].[Order] WHERE CustomerId = @CustomerId;";

    // Ensure to wrap with 'using' to auto-dispose
    using (var extractor = connection.ExecuteQueryMultiple(commandText, new { CustomerId = 10045 }))
    {
        // We know that the first query is for 'Customer' and second query is type 'int'
        var customer = extractor.Extract<Customer>().FirstOrDefault();
        var ordersCount = extractor.Scalar<int>();

        // Do the stuffs for the 'customer' and 'ordersCount' here
    }
}

Always wrap the result in a using statement to ensure proper disposal and avoid memory leaks.