Update: This seems to be fixed in Explorer Platform Preview 1.9.7766.6000.

As I’m still learning ASP.NET MVC, my solution may not be the optimal one.

Create a custom model binder that will only react differently to double values.

using System;
using System.Globalization;
using System.Web.Mvc;

namespace NerdDinner.Helpers {
  public class CustomModelBinder : DefaultModelBinder {

    public CustomModelBinder()
      : base() {
    }

    public override object BindModel(ControllerContext controllerContext, 
      ModelBindingContext bindingContext) {
      
      object result = null;

      // Don't do this here!
      // It might do bindingContext.ModelState.AddModelError
      // and there is no RemoveModelError!
      // 
      // result = base.BindModel(controllerContext, bindingContext);

      if (bindingContext.ModelType == typeof(double)) {

        string modelName = bindingContext.ModelName;
        string attemptedValue = bindingContext.ValueProvider[modelName].AttemptedValue;

        // Depending on cultureinfo the NumberDecimalSeparator can be "," or "."
        // Both "." and "," should be accepted, but aren't.
        string wantedSeperator = NumberFormatInfo.CurrentInfo.NumberDecimalSeparator;
        string alternateSeperator = (wantedSeperator == "," ? "." : ",");

        if (attemptedValue.IndexOf(wantedSeperator) == -1 
          && attemptedValue.IndexOf(alternateSeperator) != -1) {
          attemptedValue = attemptedValue.Replace(alternateSeperator, wantedSeperator);
        }

        try {
          result = double.Parse(attemptedValue, NumberStyles.Any);
        }
        catch (FormatException e) {
          bindingContext.ModelState.AddModelError(modelName, e);
        }

      }
      else {
        result = base.BindModel(controllerContext, bindingContext);
      }

      return result;
    }
  }
}

Change the DefaultBinder in Global.asax.

void Application_Start() {
  //[SNIP]
  ModelBinders.Binders.DefaultBinder = new CustomModelBinder();
}

<%
// prevent caching (asp classic jscript)
Response.CacheControl = "no-cache";
Response.AddHeader("Pragma", "no-cache");
Response.Expires = -1;
%>

<%
' prevent caching (asp classic vbscript) '
Response.CacheControl = "no-cache"
Response.AddHeader "Pragma", "no-cache"
Response.Expires = -1
%>

<?php
// prevent caching (php)
header('Cache-Control: no-cache');
header('Pragma: no-cache');
header('Expires: ' . gmdate(DATE_RFC1123, time()-1));
?>

// prevent caching (C#)
//Response.AddHeader("Cache-Control", "no-cache");
//Response.AddHeader("Pragma", "no-cache");
//Response.Expires = -1;

Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();
Response.Cache.SetExpires(DateTime.MinValue);

More information here: How to prevent caching in Internet Explorer

Compare for yourself:

• silverlight vs javascript (unchanged original)
• silverlight vs flash (js delegates all logic to flash, silverlight code unchanged)

<%@LANGUAGE="JAVASCRIPT" CODEPAGE="65001"%>
<%

function getData(connectionString, sql){
    var result = null;
    var adStateOpen = 1;
    var connection = new ActiveXObject("ADODB.CONNECTION");
    try{
        connection.Open(connectionString);
    } catch(e1){
        return null;
    }
    if (connection.State !== adStateOpen) {
        return null;
    }
    try{
        var recordset = connection.Execute(sql);
    } catch(e2){
        return null;
    }
    if (!recordset.EOF) {
        result = recordset.GetRows().toArray();
        recordset.Close();
    }
    recordset = null;
    connection.Close();
    connection = null;
    return result;
}


function writeCsvHttpHeaders(filename){
    Response.ContentType = "text/csv";
    Response.Charset = "utf-8";
    Response.AddHeader("Content-Disposition", 
            "attachment; filename="+filename+".csv");
}

function writeXlsHttpHeaders(filename){
    Response.ContentType = "application/vnd.ms-excel";
    Response.Charset = "utf-8";
    Response.AddHeader("Content-Disposition", 
            "attachment; filename="+filename+".xls");
}

function getXlsStart(){
    return ""
    + "<html>\n"
    + "<head>\n"
    + "<meta http-equiv=\"Content-Type\" "
    + "content=\"text/html; charset=UTF-8\">\n"
    + "<style type=\"text/css\">\n"
    + "html, body, table {\n"
    + "    margin: 0;\n"
    + "    padding: 0;\n"
    + "    font-size: 11pt;\n"
    + "}\n"
    + "table, th, td { \n"
    + "    border: 0.1pt solid #D0D7E5;\n"
    + "    border-collapse: collapse;\n"
    + "    border-spacing: 0;\n"
    + "}\n"
    + "</style>\n"
    + "</head>\n"
    + "<body>\n"
    + "<table>\n"
    + "";
}

function getXlsEnd(){
    return ""
    + "</table>\n"
    + "</body>\n"
    + "</html>"
    + "";
}

function csvEscape(val){
    if (typeof val === "number") {
        return val.toString(10).replace(".", ",");
    } else if (typeof val === "string") {
        if (val.indexOf("\"") !== -1) {
            return "\""+val.replace(/"/g, "\"\"")+"\"";
        } else if (val.indexOf(";") !== -1) {
            return "\""+val+"\"";
        } else {
            return val;
        }
    } else if (val === null) {
        return "#NULL#";
    } else if (val === undefined) {
        return "#UNDEFINED#";
    } else {
        return "#ERROR#";
    }
}

function writeCsv(filename, data, columnCount){
    writeCsvHttpHeaders(filename);
    // utf-8 BOM (very important for special characters)
    Response.Write("\uFEFF");
    for (var i=0, il=data.length; i<il; i+=columnCount) {
        for (var j=0; j<columnCount; j++) {
            Response.Write(csvEscape(data[i+j]));
            if (j !== columnCount-1) {
                Response.Write(";");
            }
        }
        Response.Write("\n");
        // prevent Response Buffering Limit Exceeded
        if (i % 1000 === 0) {
            Response.Flush();
        }
    }
}

function xlsEscape(val){
    if (typeof val === "number") {
        return val.toString(10).replace(".", ",");
    } else if (typeof val === "string") {
        return Server.HTMLEncode(val);
    } else if (val === null)  {
        return "#NULL#";
    } else if (val === undefined)  {
        return "#UNDEFINED#";
    } else {
        return "#ERROR#";
    }
}

function writeXls(filename, data, columnCount){
    writeXlsHttpHeaders(filename);
    Response.Write(getXlsStart());
    for (var i=0, il=data.length; i<il; i+=columnCount) {
        Response.Write("<tr>");
        for (var j=0; j<columnCount; j++) {
            Response.Write("<td>");
            Response.Write(xlsEscape(data[i+j]));
            Response.Write("</td>");
        }
        Response.Write("</tr>\n");
        // prevent Response Buffering Limit Exceeded
        if (i % 1000 === 0) {
            Response.Flush();
        }
    }
    Response.Write(getXlsEnd());
}

function main(){
    var filetype = Request.QueryString("filetype")();
    var connectionString = "Provider=SQLOLEDB.1;"
    + "Data Source=LAPTOP\\SQLEXPRESS;"
    + "User ID=internal;"
    + "Password=internal;"
    + "Initial Catalog=trees_in_sql";
    var sql = ""
    + "SELECT id \n"
    + ", name \n"
    + "FROM People \n"
    + ";";
    var filename = "filename";
    var columnCount = 2;
    
    var data = getData(connectionString, sql);
    if (data !== null) {
        Response.Clear();
        if (filetype === "csv") {
            writeCsv(filename, data, columnCount);
        } else {
            writeXls(filename, data, columnCount);
        }
    } else {
        Response.Write("Error, no data found");
    }
    Response.End();
}

main();

%>

Resources: