Question

I have a viewmodel where the properties have display names. I am now making an Excel sheet with the same data in as the grid in the webpage. I am using closed xml (which uses openxml) to create the Excelsheet on the server and send it to the webclient when they want to download data as Excel.
When I write the header row in Excel openxml stream I want to reuse the displayname that I already have defined. But I can’t figure out what to call on.

Here is an example of the display name. ( For the example I only use two, reality there are many many more columns) :

 using System.ComponentModel.DataAnnotations;
 public class DCArrival : IDCArrival
 { 
   [Display(Name = "Via Transit")]
   public String LocationType { get; set; }
   [Display(Name = "Currency")]
   String CurrencyISOCode { get;  }
 }

Then I want to use this displayname when I create the header row. Mark the pseudocode that tries to explain what I want to get hold of:

private MemoryStream CreateExcelFile(ICollection<DCArrival> dcArrToShow
, QueryStrInput   queryStrInput)
    {
        try
        {
            // Create an Excel Workbook
            XLWorkbook wb = new XLWorkbook();
            // Add the worksheet with  data 
            IXLWorksheet ws = wb.Worksheets.Add("New Worksheet");
            // Add my data that was displayed in the html table ... 
            ws.Cell(1, 1).SetValue("Hello World");
           //Add Header row. By taking a object in the collection and figure out its
           // display name
           DCArrival firstRow = dcArrToShow.First();
           // Here comes my problem. Here is my dream up mockup code

            ws.Cell(2,1).Value = firstRow.LocationType.DisplayAttribute.GetName()
            ws.Cell(2,2).Value = firstRow.CurrencyISOCode.DisplayAttribute.GetName()
           // back to reality
           //this is how easy I can get all data from Collection
            ws.Cell(3, 1).Value = dcArrToShow.AsEnumerable();
          // All done
            MemoryStream ms = new MemoryStream();
            wb.SaveAs(ms);
            return ms;
        }
        catch (Exception e)
        {
            string errmsg = String.Format("Failed to create Excel file: {0}",
          e.Message);
            throw new Exception(errmsg, e);
        }

I have looked at the http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.displayattribute.aspx
But I do not understand how I get a hold of it.
I understand that this is magically fixed for you when you are using normal mvc 3 html rendering. When I Google these concepts I get drowned in blogs who wants to explain basic validation in MVC 3.

Answer 1

You could retrieve it from the model metadata:

ws.Cell(2.1).Value = ModelMetadata.FromLambdaExpression<DCArrival, string>(x => x.LocationType, new ViewDataDictionary<DCArrival>(firstRow)).DisplayName;

or write an extension method:

public static class ModelMetadataExtensions
{
    public static string GetName<TModel, TProperty>(this TModel model, Expression<Func<TModel, TProperty>> ex)
    {
        return ModelMetadata
            .FromLambdaExpression<TModel, TProperty>(ex, new ViewDataDictionary<TModel>(model))
            .DisplayName;
    }
}

and then:

ws.Cell(2.1).Value = firstRow.GetName(x => x.LocationType);
ws.Cell(2.2).Value = firstRow.GetName(x => x.CurrencyISOCode);

---

UPDATE:

As per a new requirement that was expressed in the comments section in order to loop through all properties and read the display attribute you could use the following:

var properties = typeof(DCArrival).GetProperties(); 
foreach (var property in properties) 
{
    var displayAttribute = property
        .GetCustomAttributes(typeof(DisplayAttribute), true)
        .FirstOrDefault() as DisplayAttribute;
    string displayName = property.Name;
    if (displayAttribute != null)
    {
        displayName = displayAttribute.Name;
    }

    // TODO: do something with the display name for this property
}