Created Issue: WebGrid paging/sorting url generated incorrectly if url has repeated querystring keys [635]

Repro:

- Create an Action method as follows that displays a WebGrid with paging enabled:

public class MyController : Controller
{
...
public ActionResult MyAction(IList<int> productId)
{
.... return a View that contains a WebGrid with paging or sorting enabled
}
}

- Navigate to the action with the following URL:

http://servername/MyController/MyAction?productId=1&productId=3&productId=5

- Examine the paging or sorting urls in the rendered WebGrid

Expected result:

- Generated urls should contain the same repeated keys as the original url, e.g.:

http://servername/MyController/MyAction?productId=1&productId=3&productId=5&page=2

Actual result:

- Generated urls replace repeated querystring keys by a single key with a comma-separated value, e.g.:

http://servername/MyController/MyAction?productId=1%2c3%2c5&page=2

- As a consequence, the productId parameter of the Action method received a single value "1,3,5" instead of a list of values.

Analysis:

This is a bug in the method WebGrid.GetPath, which does not take account of repeated values in the QueryString NameValueCollection. To fix it, replace the following code:

for (int i = 0; i < queryString.Count; i++)
{
if (i > 0)
{
sb.Append("&");
}
sb.Append(HttpUtility.UrlEncode(queryString.Keys[i]));
sb.Append("=");
sb.Append(HttpUtility.UrlEncode(queryString[i]));
}

with something like:

for (int i = 0; i < queryString.Count; i++)
{
string encodedKey = HttpUtility.UrlEncode(queryString.Keys[i]);
foreach(string value in queryString.GetValues(i))
{
if (i > 0)
{
sb.Append("&");
}
sb.Append(key);
sb.Append("=");
sb.Append(HttpUtility.UrlEncode(value));
}
}