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POI am wondering about the state of connection and impact on code performance by 'yield' while iterating over data reader object
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  1. POI am wondering about the state of connection and impact on code performance by 'yield' while iterating over data reader object
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    copied!<p>Here is my sample code that I am using to fetch data from database: on DAO layer:</p> <pre><code>public IEnumerable&lt;IDataRecord&gt; GetDATA(ICommonSearchCriteriaDto commonSearchCriteriaDto) { using(DbContext) { DbDataReader reader = DbContext.GetReader("ABC_PACKAGE.GET_DATA", oracleParams.ToArray(), CommandType.StoredProcedure); while (reader.Read()) { yield return reader; } } } </code></pre> <p>On BO layer I am calling the above method like:</p> <pre><code>List&lt;IGridDataDto&gt; GridDataDtos = MapMultiple(_costDriversGraphDao.GetGraphData(commonSearchCriteriaDto)).ToList(); </code></pre> <p>on mapper layer MapMultiple method is defined like:</p> <pre><code>public IGridDataDto MapSingle(IDataRecord dataRecord) { return new GridDataDto { Code = Convert.ToString(dataRecord["Code"]), Name = Convert.ToString(dataRecord["Name"]), Type = Convert.ToString(dataRecord["Type"]) }; } public IEnumerable&lt;IGridDataDto&gt; MapMultiple(IEnumerable&lt;IDataRecord&gt; dataRecords) { return dataRecords.Select(MapSingle); } </code></pre> <p>The above code is working well and good but I am wondering about two concerns with the above code. </p> <ol> <li>How long data reader’s connection will be opened?</li> <li>When I consider code performance factor only, Is this a good idea to use ‘yield return’ instead of adding record into a list and returning the whole list? </li> </ol>
 

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