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Dynamic list creation

Posted on 2009-04-14
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Last Modified: 2013-12-17
Greetings all

I have a method that returns the results of stored procedure, selected by the user. I would like to return that data to the UI layer via a generic list. The problem is that I have no way of knowing how many fields or what type comes back.

Is this possible using a List/Class in a similiar way to the attached snippet (this is just an example of a simple case) ??


In advance, thanks!!!

    allanamrk
SAMPLE CLASS
 
List<EMailAddress> emailContacts = new List<EMailAddress>();
 
using System;
using System.Collections.Generic;
using System.Text;
 
namespace DataTransferObjects
{
    public class EMailAddress
    {
 
        private string name;
        private string email;
        
        public EMailAddress()
        {
 
        }
 
        public EMailAddress(string pName, string pEmail)
        {
            name = pName;
            email = pEmail;
        }
 
        public string Name
        {
            get { return name; }
            set { name = value; }
        }
 
        public string Email
        {
            get { return email; }
            set { email = value; }
        }
 
    }
}

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Question by:allanmark
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14 Comments
 
LVL 27

Expert Comment

by:Dabas
ID: 24145856
What about returning a list of DataRows?

List<DataRow> MyDataRowList = new List<DataRow>();

Dabas
0
 

Author Comment

by:allanmark
ID: 24145960
I tried that, but I need to work with the data in a GridView. When I linked the List (of DataRow) to the grid, it complained that there was no DATAFIELD - what I had was a list of array.
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Expert Comment

by:Dabas
ID: 24146059
Show me the code where you bind to the grid
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Author Comment

by:allanmark
ID: 24146098
queryResults =
    BusinessLogic.Business.GetQueryResults(.......);

// Binding
gvResults.DataSource = queryResults;
 gvResults.DataBind();
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LVL 27

Expert Comment

by:Dabas
ID: 24146689
And the code for GetQueryResults?
0
 

Author Comment

by:allanmark
ID: 24146843
Ooops!!!

Sorry!  I'm having a really blonde day!! (no offense intended, if you happen to be blonde!!!).


 public static List<DataRow> GetQueryResults(string procName, List<DbParam> dbParms, string [] fieldNames)
        {
            List<DataRow> queryResults = new List<DataRow>();
 
            queryResults = DataAccess.ReturnQueryResults(procName, dbParms);
 
            return queryResults;
        }
 
 
public static List<DataRow> ReturnQueryResults(string procName, List<DbParam> dbParms)
{
            List<DataRow> returnedRecords = new List<DataRow>();
                        
            SqlParameter workParam;
 
            SqlConnection sqlConn = new SqlConnection(connectStr);
 
            DataSet dsQuery = new DataSet();
                   
            SqlDataAdapter daQuery = new SqlDataAdapter(procName, sqlConn);
            daQuery.SelectCommand.CommandType = CommandType.StoredProcedure;
 
            if (dbParms.Count > 0)
            {
                foreach (DbParam parm in dbParms)
                {
                    workParam = GetParameter(parm.ParmName, parm.ParmType, parm.ParmVal);
                    daQuery.SelectCommand.Parameters.Add(workParam);
                }
            }
         
            daQuery.Fill(dsQuery, "QueryResults");
 
            List <DataRow> returnedRecords = new List<DataRow>(dsQuery.Tables["QueryResults"].Select());
 
            return returnedRecords;
}

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Accepted Solution

by:
Dabas earned 300 total points
ID: 24146906
Thanks

I suggest that you try filling a DataTable instead of a DataSet
Then instead of returning a List of rows, return the DataTable.

DataGridViews work very well with DataTables

Dabas
0
 

Author Comment

by:allanmark
ID: 24147112
COuld do that.
It's just that we have been encouraged to work with Lists, so as to achieve independance/separattion between the DataLayer and the UI and also to n=minimise reliance on System.Data.

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LVL 27

Expert Comment

by:Dabas
ID: 24147235
It could be the right approach, except for your statement 'The problem is that I have no way of knowing how many fields or what type comes back'

I do not see anything wrong with reliance on System.Data. The same can be argued against reliance on System.Collections.

Dabas
0
 

Author Comment

by:allanmark
ID: 24147348
Ok.

So maybe what I need to do is work with the lists, where I have a definite structure that is returned and where it is something flexible / unknown (shoudl only be this one case) return a datatable.

Does that sound like an acceptable "work-around" compromsie, to you?
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LVL 27

Expert Comment

by:Dabas
ID: 24147363
Yes
0
 

Author Closing Comment

by:allanmark
ID: 31569876
Many thanks!!!
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