Returns DbDataReader when SqlDataCommand.ExecuteReader()

Question

I am writing a function to read data from sql database, the function is as follows,

public override Dictionary<string, DbDataReader> GetData()
{
    using (_connection)
    {
        Dictionary<string, DbDataReader> dataDictionary = new Dictionary<string, DbDataReader>();
        _xmlDoc.Load("Queries.xml");
        XPathNavigator navigator = _xmlDoc.CreateNavigator();
        XPathNodeIterator iterator = navigator.Select("//query");
        while (iterator.MoveNext())
        {
            _command = new SqlCommand(iterator.Current.ToString());
            _command.Connection = _connection;
            _command.CommandText = iterator.Current.ToString();
            SqlDataReader reader = _command.ExecuteReader();

            dataDictionary.Add(iterator.Current.GetAttribute("name", ""), reader);
        }
        return dataDictionary;
    }
}

But I get a complier error, stating:

Cannot convert source type 'system.data.common.dbdatareader' to target type 'system.data.sqlclient.sqldatareader '

But I check the MSDN: https://msdn.microsoft.com/en-us/library/9kcbe65k(v=vs.110).aspx

Where it says that the return type of ExecuteReader() is 'system.data.sqlclient.sqldatareader'

Can anybody help me? Thank you!

Kalpesh Satasiya · Accepted Answer · 2015-10-26 11:01:56Z

Update your code replace DbDataReader to IDataReader..

public Dictionary<string, IDataReader> GetData()
    {
        using (_connection)
        {
            Dictionary<string, IDataReader> dataDictionary = new Dictionary<string, IDataReader>();
            _xmlDoc.Load("Queries.xml");
            XPathNavigator navigator = _xmlDoc.CreateNavigator();
            XPathNodeIterator iterator = navigator.Select("//query");
            while (iterator.MoveNext())
            {
                _command = new SqlCommand(iterator.Current.ToString());
                _command.Connection = _connection;
                _command.CommandText = iterator.Current.ToString();
                IDataReader reader = _command.ExecuteReader();

                dataDictionary.Add(iterator.Current.GetAttribute("name", ""), reader);
            }
            return dataDictionary;
        }

    }

Damien_The_Unbeliever · Accepted Answer · 2015-10-26 11:06:48Z

1

Your method is looking for a return type of Dictionary<string, DbDataReader> but you are returning Dictionary<string, SqlDataReader>.

public override Dictionary<string, DbDataReader> GetData()
{
    using (_connection)
    {
         Dictionary<string, DbDataReader> dataDictionary = new Dictionary<string, DbDataReader>();
         xmlDoc.Load("Queries.xml");
         XPathNavigator navigator = _xmlDoc.CreateNavigator();
         XPathNodeIterator iterator = navigator.Select("//query");
         while (iterator.MoveNext())
         {
             DbCommand _command = db.GetSqlStringCommand(iterator.Current.ToString());
             IDataReader dataReader = db.ExecuteReader(_command);

              dataDictionary.Add(iterator.Current.GetAttribute("name", ""), dataReader);
         }
         return dataDictionary;
   }
}

edited Oct 26, 2015 at 11:06

Damien_The_Unbeliever

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answered Oct 26, 2015 at 10:36

Stephen Brickner

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5 Comments

Gravity Over a year ago

Even I changed the signature, this error still exists. And the reason why I use this signature is because I want to override a base function, so that I can do the same executions with sql and oracle databases. Like stated in : stackoverflow.com/questions/33341435/…

Stephen Brickner Over a year ago

I didn't notice you were overriding a method. So basically then you can't add the SqlDataReader to dictionary like you are in the while loop. It would have to be a DbDataReader.

Stephen Brickner Over a year ago

I made an update to the code. That should return you the proper type.

Gravity Over a year ago

Thank you! But what is the type of db?

Stephen Brickner Over a year ago

It's of type Database db. It's like your SqlConnection class. You may just be able to use SqlConnection and SqlCommand still and just use the IDataReader to read the sql command.

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