Recently, I needed to export some data into a CSV file. Curiously, there is no CSV support in Asp.Net MVC and writing your custom ActionResult is quite simple.
Here is mine, if this can save you some times:
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/// <summary>
/// ActionResult specialized in CSV file.
/// </summary>
public sealed class CSVResult<T> : System.Web.Mvc.FileResult
{
private IEnumerable<T> collection;
private String[] columnsToExclude;
public CSVResult(IEnumerable<T> collection, params String[] columnsToExclude) : base("text/csv")
{
this.collection = collection;
this.columnsToExclude = columnsToExclude;
}
protected override void WriteFile(HttpResponseBase response)
{
System.IO.Stream outputStream = response.OutputStream;
using (MemoryStream mstream = new MemoryStream())
{
WriteObject(mstream);
outputStream.Write(mstream.GetBuffer(), 0, (int) mstream.Length);
}
}
private void WriteObject(Stream stream)
{
// We will follow the recommandations stated in this article
// http://www.commentcamarche.net/faq/sujet-7273-exporter-a-coup-sur-du-csv
// - embedding all values in quotes
// - double quote literal values
// - add \n\r between each lines.
StreamWriter writer = new StreamWriter(stream, System.Text.Encoding.Default);
// Render columns
Type modelType = typeof(T);
List<ModelMetadata> metadatas = ModelMetadataProviders.Current.GetMetadataForProperties(null, modelType).ToList();
for(int i=0; i<metadatas.Count; )
{
if (Array.IndexOf<String>(columnsToExclude, metadatas[i].PropertyName) != -1)
metadatas.RemoveAt(i);
else
{
WriteValue(writer, metadatas[i].DisplayName ?? metadatas[i].PropertyName);
i++;
}
}
writer.WriteLine();
// Render data
var en = collection.GetEnumerator();
while (en.MoveNext())
{
ModelMetadata mprop = ModelMetadataProviders.Current.GetMetadataForType(() => en.Current, modelType);
foreach(ModelMetadata prop in mprop.Properties)
{
WriteValue(writer, prop.SimpleDisplayText ?? String.Empty);
}
writer.WriteLine();
}
writer.Flush();
}
private static void WriteValue(StreamWriter writer, String literal)
{
// Enclose values in quote
writer.Write("\"");
string line = literal.Replace("\"", "\"\"");
writer.Write(line);
writer.Write("\";");
}
}
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Usage:
We have a simple ViewModel that contains the Password property for import usage but it is hide in export context.
This is the purpose of the columnsToExclude parameter.
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ViewModel
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/// <summary>
/// Represents a user as it stands in import/export CSV.
/// </summary>
public class CSVUserModel
{
[Display(Order = 0)]
public String Account { get; set; }
[Display(Order = 1)]
public String FullName { get; set; }
[Display(Order = 2)]
public String Password { get; set; }
[Display(Order = 3)]
public String Email { get; set; }
[Display(Order = 4)]
public Boolean IsAdmin { get; set; }
[Display(Order = 5)]
public Boolean IsActive { get; set; }
}
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Your controller:
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...
public ActionResult ExportCSV()
{
var users = storeDB.Users;
List<CSVUserModel> exportedUser = new List<CSVUserModel>();
foreach (var user in users)
{
MembershipUser fbaUser = Membership.GetUser(user.FbaUserId);
exportedUser.Add(new CSVUserModel {
Account = fbaUser.UserName,
FullName = user.Name,
Email = user.Email,
IsAdmin = user.IsAdmin,
IsActive = user.IsActive
});
}
return new CSVResult<CSVUserModel>(exportedUser, "Password") { FileDownloadName = "users.csv" };
}
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