Question

I am working on a Silverlight application using a WCF service where I need to get all the Column Headers from a specific table. I have been trying to write a LINQ query to do this, but so far I have not been able to get it to work correctly. I have not found very much information pertaining to this. I have found the following information, but I have had difficulties connecting to my data.

http://www.c-sharpcorner.com/UploadFile/dhananjaycoder/4856/#ReadAndPostComment

So far I have tried the following…This will not compile due to DataContext needing a parameter and that is where I am stuck.

public List<string> GetColumnHeaders()
{
    DataContext context = new DataContext();
    List<string> columnList = new List<string>();
    var dataModel = context.Mapping;

    foreach (var r in dataModel.GetTables())
    {
        if (r.TableName.Equals("table1", StringComparison.InvariantCultureIgnoreCase))
        {
            foreach (var c in r.RowType.DataMembers)
            {
                columnList.Add(c.MappedName);
            }
        }
    }
    return columnList;
}

Instead of using DataContext context = new DataContext();
I tried the following, but I know the problem is the same.

var dataModel = new AttributeMappingSource()
                 .GetModel(
                      typeof(RepositoryBase<HBS_SondesEntities>
                 ));

Answer 1

Here is my best attempt at a solution, its hard to really understand what you have tried/written.

public List<string> GetColumnHeaders(){
  List<string> columnList = new List<string>();
  using (SondesEntities context = new HBS_SondesEntities()){
    foreach (var r in context.Mapping.GetTables()){
       if (r.TableName
             .Equals("table1", StringComparison.InvariantCultureIgnoreCase)) {

           foreach (var c in r.RowType.DataMembers){
               columnList.Add(c.MappedName);
           }
       }
     }
  }
  return columnList;
}

---

Assuming I didn’t fat finger something here is the same code using linq.

public List<string> GetColumnHeaders(){

    List<string> columnList = new List<string>();
    using (SondesEntities context = new HBS_SondesEntities()){
        var query = (
           context.Mapping.GetTables()
             .Where(t=>t.TableName
                        .Equals(
                         "table1", 
                          StringComparison.InvariantCultureIgnoreCase)
                        )
             ).SelectMany(x=>x.RowType.DataMembers);

        columnList  = query.Select(m=>m.MappedName).ToList()
    }
    return columnList;
}