https://learn.microsoft.com/en-us/dotnet/api/microsoft.data.sqlclient.sqlcommand.endexecutereader?view=sqlclient-dotnet-standard-5.2
SqlCommand.EndExecuteReader(IAsyncResult) Method (Microsoft.Data.SqlClient) | Microsoft Learn
Finishes asynchronous execution of a Transact-SQL statement, returning the requested SqlDataReader .
microsoft datasqlcommandiasyncresultmethodsqlclient