[API Proposal]: Add Async Methods to IDataReader

[RAAvenger]

Background and motivation

I'm writing a code that exposes an NpgsqlDataReader. I would like to use async methods of DataReader and also be able to test my code by mocking DataReader, so i prefer to expose an IDataReader that can be mocked but if i do this i can't use async methods. Of course there is workaround like writing wrapper and ... but it would be great if the interface contains async methods.

API Proposal

namespace System.Data
{
    public interface IDataReader : IDisposable, IDataRecord
    {
        int Depth { get; }
        bool IsClosed { get; }
        int RecordsAffected { get; }
        void Close();
        Task CloseAsync();
        DataTable? GetSchemaTable();
        Task<DataTable?> GetSchemaTableAsync(CancellationToken cancellationToken);
        bool NextResult();
        Task<bool> NextResultAsync(CancellationToken cancellationToken);
        bool Read();
        Task<bool> ReadAsync(CancellationToken cancellationToken);
    }
}

API Usage

var connection = new NpgsqlConnection(connectionString);
await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
var command = connection.CreateCommand();
command.CommandText = query;
IDataReader reader = await command.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
while(await reader.ReadAsync(connectionString).ConfigureAwait(false))
{
// get data
}

Alternative Designs

No response

Risks

No response

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Issue Details

---

Background and motivation

I'm writing a code that exposes an NpgsqlDataReader. I would like to use async methods of DataReader and also be able to test my code by mocking DataReader, so i prefer to expose an IDataReader that can be mocked but if i do this i can't use async methods. Of course there is workaround like writing wrapper and ... but it would be great if the interface contains async methods.

API Proposal

namespace System.Data
{
    public interface IDataReader : IDisposable, IDataRecord
    {
        int Depth { get; }
        bool IsClosed { get; }
        int RecordsAffected { get; }
        void Close();
        Task CloseAsync();
        DataTable? GetSchemaTable();
        Task<DataTable?> GetSchemaTableAsync(CancellationToken cancellationToken);
        bool NextResult();
        Task<bool> NextResultAsync(CancellationToken cancellationToken);
        bool Read();
        Task<bool> ReadAsync(CancellationToken cancellationToken);
    }
}

API Usage

var connection = new NpgsqlConnection(connectionString);
await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
var command = connection.CreateCommand();
command.CommandText = query;
IDataReader reader = await command.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
while(await reader.ReadAsync(connectionString).ConfigureAwait(false))
{
// get data
}

Alternative Designs

No response

Risks

No response

Author:	RAAvenger
Assignees:	-
Labels:	api-suggestion, area-System.Threading.Tasks
Milestone:	-

[svick]

Just adding methods to an interface is a massive breaking change, so it's not going to happen.

Adding them as default interface methods is much less of a breaking change, but then the question becomes what the default implementation should be and I'm not sure there is a good answer to that.

Can't you mock DbDataReader for your tests instead?

[RAAvenger]

thanks for your suggestion. using DbDataReader will resolve my issue.
A non-breaking option that comes to mind is to define a new Interface (e.g. IAsyncDataReader) for all those async method overloads of DbDataReader class and let DbDataReader implement the aforementioned interface alongside the existing IDataReader