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POWhat is a good Mapper pattern for information stored in an ini file?
 

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  1. POWhat is a good Mapper pattern for information stored in an ini file?
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    <p>When designing an n-tier application, I tend to use a pattern adopted and adapted from Lhotka's CSLA framwork. In a nutshell, the Repository layer populates a SqlDataReader and passes the data reader, the instance to be mapped, and the mapping information to the Mapper layer which then populates the instance. </p> <p>This pattern has proved itself over and again in many projects I have worked on for a number of reasons:</p> <ol> <li>It is easy to understand and implement, developers tend to stick to it because they understand what it is doing.</li> <li>It enables very easy reuse of the mappers for inherited classes and well as composite classes.</li> <li>Any changes in the entity, and therefore the mapper assigned to it, cause compile time errors pointing directly to the stored procs that also need to be changed.</li> </ol> <p>Here is some sample repository code:</p> <pre><code>internal static List&lt;CompositeEntities.ContactReportRpa&gt; RetrieveByReportId(int reportId) { CompositeEntities.ContactReportRpa report = null; List&lt;CompositeEntities.ContactReportRpa&gt; reports = new List&lt;CompositeEntities.ContactReportRpa&gt;(); using (SqlConnection conn = DBConnection.GetConnection()) { cmd.Connection = conn; cmd.CommandType = System.Data.CommandType.StoredProcedure; cmd.CommandText = "ContactReportRpa_SEL_ByIdReport"; cmd.Parameters.Add("@IdReport", System.Data.SqlDbType.Int).Value = reportId; conn.Open(); using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { report = new CompositeEntities.ContactReportRpa(); ContactReportRpaMapper.Map("IdReportRpa", "IdReport", "IdRecommendation", "IsDisplayed", "Comments", report.Rpa, reader); RpaRecommendationMapper.Map("IdRecommendation", "IdDepartment", "TitleRecommendation", "Description", "DisplayOrderRecommendation", report.Recommendation, reader); RpaDepartmentMapper.Map("IdDepartment", "TitleDepartment", "DisplayOrderDepartment", report.Department, reader); reports.Add(report); } } } return reports; } </code></pre> <p>Here is some sample Mapper Code. It is pretty straightforward: The mapper knows which class property gets mapped to each field in the data reader. The name of each field is passed to the mapper so the same mapper can be used regardless of the names assigned to each field in the sproc.</p> <pre><code>internal static void Map(string fieldId, string fieldName, string fieldDisplayOrder, RpaDepartment entity, SqlDataReader reader) { entity.Id = reader.GetInt32(reader.GetOrdinal(fieldId)); entity.Title = reader.GetString(reader.GetOrdinal(fieldName)); entity.DisplayOrder = reader.GetInt32(reader.GetOrdinal(fieldDisplayOrder)); } </code></pre> <p>So my question is this: How should I implement this pattern when the data source is a text file? I want to stick with this pattern because eventually the data source will be migrated to a db. </p> <p>Any suggestions?</p> <p>EDIT: The ini files already exist and I do not have the go ahead to change them at this time. So I am stuck with them for now.</p>
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    1. COCan you edit the question to explain how the mapper pattern works a little more? Also, it would be useful to see how your entities/relations and ini files will be structured, since ini files don't have the same sorts of hierarchy as DB tables/result sets. (and you might have better luck with XML files - it is easier to build a data hierarchy in those, and you can use the .Net built-in XML serializer to populate your objects)
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      1. USMerlyn Morgan-Graham
    2. CO@MerlynMorgan-Graham: I just added the mapper function for the RpaDepartment class. Regarding the hierarchy, it's easy. There is none in this case :)
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      1. POWhat is a good Mapper pattern for information stored in an ini file?
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    3. COWouldn't the implementation of the pattern depend on the "shape" of the original data source? In that case, the format of the text file would be relevant. You'll also need to make an abstraction over `SqlDataReader` to a generic source of named fields that are convertible to basic types, and implement that for the given text file format.
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