Question

Answer Summary:

Solved this problem using Jon Skeet’s answer below. Here is the finished code

    public static CSVData CreateCSVData(List<RegDataDisplay> rList, 
                                                         string[] selectors)
    {
        CSVData csv = new CSVData(); // Create the CSVData object
        foreach(string selector in selectors)
        {
            // Get the PropertyInfo for the property whose name
            // is the value of selector
            var property = typeof(RegDataDisplay).GetProperty(selector); 

            // Use LINQ to get a list of the values for the specified property
            // of each RegDataDisplay object in the supplied list.
            var values = rList.Select(row => property.GetValue(row, null)
                              .ToString());

            // Create a new list with the property name to use as a header
            List<string> templs = new List<string>(){selector};

            // Add the returned values after the header 
            templs.AddRange(values);

            // Add this list as a column for the CSVData object.
            csv.Columns.Add(templs);
        }
        return csv;
    }

Question

I am building my SQL query dynamically from user input, and then exporting the results to a CSV file. I have a class called RegDataDisplay which has a property for each of the possible columns returned by my query. I can tell what columns are being selected but in my CSV creator I need to be able to only output those specific columns.

In the example below, all of the data I have retrieved is in rList, and the names of the properties I need are in selectors. So I want to iterate through the list and then add only the properties I need to my CSV data.

public static CSVData CreateCSVData(List<RegDataDisplay> rList, string[] selectors)
{ 
    CSVData csv = new CSVData();
    for(int i = 0; i < selectors.Length; i++)
    {
        csv.Columns.Add(new List<string>(){selectors[i]});
    }

    // So now I have the headers for the CSV columns, 
    // I need the specific properties only which is where I'm stuck

    for(int i = 0; i < selectors.Length; i++)
    {
        for(int j = 0; j < rList.Count; j++)
        {
            // If it was javascript I would do something like this 

            csv.Columns[i].Add(rList[j][selectors[i]]);

        } 
    }
}

Thanks

EDIT: On the right track now but I’m coming up against an error “Object does not match target type”.

    public static CSVData CreateCSVData()
    {
        // I've created a test method with test data

        string[] selectors = new string[] { "Firstname", "Lastname" };
        List<RegDataDisplay> rList = new List<RegDataDisplay>();
        RegDataDisplay rd = new RegDataDisplay();
        rd.Firstname = "first";
        rd.Lastname = "last";
        rList.Add(rd);

        CSVData csv = new CSVData();
        foreach(string selector in selectors)
        {
            var property = typeof(RegDataDisplay).GetProperty(selector);
            var values = rList.Select(row => property.GetValue(rList, null).ToString())
                              .ToList(); // Error throws here
            csv.Columns.Add(values);
        }
        return csv;
    }

Answer 1

Assuming you’re on .NET 3.5 or higher, it sounds like you may want something like:

public static CSVData CreateCSVData(List<RegDataDisplay> rList,
                                    string[] selectors)
{ 
    CSVData csv = new CSVData();
    foreach (string selector in selectors)
    {
        var prop = typeof(RegDataDisplay).GetProperty(selector);
        var values = rList.Select(row => (string) prop.GetValue(row, null))
                          .ToList();
        csv.Columns.Add(values);
    }
}