SqlMapper.GridReader constructor is internal and prevents mocking

[dreymers-goformz]

It would be great if the SqlMapper.GridReader constructor were changed to be public - then I'd be able to include QueryMultiple with the rest of my mocking for Dapper in my unit and integration tests.

[Debbus72]

If there is a good reason to keep the constructor internal then please say so and close this issue. The issue is now like 1,5 years open...
If there is a good way to mock the SqlMapper.GridReader that we can use (we use Moq), please also say so...

[dreymers-goformz]

Since my original post, I've added a wrapper class around everything Dapper, and set up my tests to mock against that.

[ESSAdeveloper]

@dreymers-goformz I am having the same issue. Can you please post a couple of examples you wrote to wrap Dapper?

[Z-Zhao]

@dreymers-goformz I am having the same issue. Can you please post a couple of examples you wrote to wrap Dapper?

This is my approach and example code of wrapper. Please have a look at my comments and the below links.
UnoSD/Moq.Dapper#85 (comment)
https://makolyte.com/csharp-how-to-unit-test-code-that-uses-dapper/

Then you could build Wrappers for QueryMultiple:
Please note the 1st Wrapper method that returns GridReader is still not be able to Mocked (because you can not construct it). But the 2nd method which has 2 types <T1, T2> can be mocked, because it returns a List that contains 2 items, and each item is a list.
You could keep going and create more methods for <T1, T2, T3> or more record sets. As long as the developer team has an agreement that there is no more than n Record sets, you can always stop at <T1, T2,... Tn>, and I assume that n won't be too large.

I can think of 2 cons of this approach:

1. the returned type is List<List<object>>, and you have to cast each item to the expected List<T1>, List<T2>... when you retrieve it.
2. the wrapper methods execucte GridReader.Read() 2 times, pre-load all of them and save all in a list. So when you have large data sets and many records in each data set, this could potentially cause performance issue.

Interface IDapperWrapper

// A wrapper to convert Dapper's static extention SQL execution methods (in its static partial class SqlMapper) to non-static methods
public interface IDapperWrapper
{

// Execute a command that returns multiple result sets as a GridReader object, and access each in turn.
GridReader QueryMultiple(IDbConnection cnn, string sql, object? param = null, IDbTransaction? transaction = null, int? commandTimeout = null, CommandType? commandType = null);

// Execute a command that returns 2 result sets as a list that contains 2 list items, and access each in turn.
// T1: First mapping object type.
// T2: Second mapping object type.
IEnumerable<IEnumerable<object>> QueryMultiple<T1, T2>(IDbConnection cnn, string sql, object? param = null, IDbTransaction? transaction = null, int? commandTimeout = null, CommandType? commandType = null);

}

The DapperWrapper class

public class DapperWrapper : IDapperWrapper
{
public GridReader QueryMultiple(IDbConnection cnn, string sql, object? param = null, IDbTransaction? transaction = null, int? commandTimeout = null, CommandType? commandType = CommandType.StoredProcedure)
{
return cnn.QueryMultiple(sql, param, transaction, commandTimeout, commandType);
}

public IEnumerable<IEnumerable<object>> QueryMultiple<T1, T2>(IDbConnection cnn, string sql, object? param = null, IDbTransaction? transaction = null, int? commandTimeout = null, CommandType? commandType = null)
{
    GridReader multi = cnn.QueryMultiple(sql, param, transaction, commandTimeout, commandType);
    List<IEnumerable<object>> list = new List<IEnumerable<object>>();
    IEnumerable<T1> t1List = multi.Read<T1>();
    IEnumerable<T2> t2List = multi.Read<T2>();
    list.Add(t1List as IEnumerable<object>);
    list.Add(t2List as IEnumerable<object>);
    return list;
}

}