Question

Let’s assume an aspx page gets multiple querystrings, for example books.aspx?author=Arthor&level=4&year=2004.

I’d like to create a button that clears specific querystring.

For example when clearAuthorBtn is clicked, user should be redirected to books.aspx?level=4&year=2004

How can I make it?
Thank you very much.

Answer 1

Here is a method that may help. I have not tested this particular implementation, but something like it should suffice (and be fairly robust).

public static string GetQueryStringWithoutKey(HttpRequest request, string keyToRemove) {

    // Assert keyToRemove is not null.
    if (keyToRemove == null) {
        throw new ArgumentNullException("keyToRemove");
    }

    // If the QueryString has no data, simply return an empty string.
    if (request.QueryString.AllKeys.Length == 0) {
        return string.Empty;
    }

    // Reconstruct the QueryString with everything except the existing key/value pair.
    StringBuilder queryStringWithoutKey = new StringBuilder();
    for (int i = 0; i < request.QueryString.AllKeys.Length; i++) {

        // Only append data that is not the given key/value pair.
        if (request.QueryString.AllKeys[i] != null &&
            request.QueryString.AllKeys[i].ToLower() != keyToRemove.ToLower()) {
            queryStringWithoutKey.Append(request.QueryString.AllKeys[i]);
            queryStringWithoutKey.Append("=");
            queryStringWithoutKey.Append(request.QueryString[i]);
            queryStringWithoutKey.Append("&");
        }
    }

    // We might have had a key, but if the only key was Message, then there is no
    // data to return for the QueryString.
    if (queryStringWithoutKey.Length == 0) {
        return string.Empty;
    }

    // Remove trailing ampersand.
    return queryStringWithoutKey.ToString().TrimEnd('&');
}

You can call the above method like this (note that I use HttpContext.Current in case you want to call this outside of an Page or UserControl):

HttpRequest request = HttpContext.Current.Request;
string url = request.ServerVariables["PATH_INFO"];
string queryString = GetQueryStringWithoutKey(request, "author");
if (!string.IsNullOrEmpty(queryString) {
    url += "?" + queryString;
}
HttpContext.Current.Response.Redirect(url);