How can I use Dapper's strongly-typed query pa

问题:

Dapper can pass query parameters as anonymous objects, and supports any ADO.NET data provider. However, when running the following query against the Sybase 15 ADO.NET drivers:

using (var connection = new AseConnection("..."))
{
    connection.Open();

    var results = connection.Query<Foo>(
        "dbo.sp_columns", new { table_name = "dbo.sysusers"}, 
        commandType: CommandType.StoredProcedure);
}

... the following error is thrown:

Sybase.Data.AseClient.AseException: Procedure sp_columns expects parameter @table_name, which was not supplied.

at Sybase.Data.AseClient.AseCommand.ᜁ(Int32 A_0)
at Sybase.Data.AseClient.AseCommand.ᜄ()
at Sybase.Data.AseClient.AseCommand.ᜀ(CommandBehavior A_0)
at Sybase.Data.AseClient.AseCommand.System.Data.IDbCommand.ExecuteReader()
at Dapper.SqlMapper.<QueryInternal>d__13`1.MoveNext() in SqlMapper.cs: line 579
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList(IEnumerable`1 source)
at Dapper.SqlMapper.Query(IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in SqlMapper.cs: line 536

Changing it to a Dapper DynamicParameters set with "@table_name" also doesn't work.

How can I pass strongly-typed parameters to Sybase with Dapper?

回答1:

As far as I can tell, the reason seems to be something to do with Sybase's AseParameter class, and not correctly mapping DbType to AseDbType values.

You can work around the problem by defining a custom Dapper IDynamicParameters set, and populating it with AseParameter objects directly:

public class AseCommandParameters : List<AseParameter>, SqlMapper.IDynamicParameters
{
    public void AddParameters(IDbCommand command, SqlMapper.Identity identity)
    {
        foreach (var parameter in this)
            command.Parameters.Add(parameter);
    }
}

And then passing an instance into the query:

using (var connection = new AseConnection("..."))
{
    connection.Open();

    var parameters = new AseCommandParameters
    {
        new AseParameter("@table_name", "dbo.sysusers")
    };

    var results = connection.Query<Foo>("dbo.sp_columns", parameters, 
        commandType: CommandType.StoredProcedure);
}

This works, and also lets you specify the AseDbType for each parameter.