CODEWITHSUNDEEP
c#asp.netquery-string
developer747
developer747

Reputation: 15928

How to update querystring in C#?

Somewhere in the url there is a &sortBy=6 . How do I update this to &sortBy=4 or &sortBy=2 on a button click? Do I need to write custom string functions to create the correct redirect url?

If I just need to append a query string variable I would do

string completeUrl = HttpContext.Current.Request.Url.AbsoluteUri + "&" + ...
Response.Redirect(completeUrl);

But what I want to do is modify an existing querystring variable.

Upvotes: 48

Views: 114146

Answers (11)

Ahmad Mageed
Ahmad Mageed

Reputation: 96477

To modify an existing QueryString value use this approach:

var nameValues = HttpUtility.ParseQueryString(Request.QueryString.ToString());
nameValues.Set("sortBy", "4");
string url = Request.Url.AbsolutePath;
Response.Redirect(url + "?" + nameValues); // ToString() is called implicitly

I go into more detail in another response.

Upvotes: 125

user2832159
user2832159

Reputation: 51

Based on Ahmad Solution I have created following Method that can be used generally

private string ModifyQueryStringValue(string p_Name, string p_NewValue)
{

    var nameValues = HttpUtility.ParseQueryString(Request.QueryString.ToString());
    nameValues.Set(p_Name, p_NewValue);
    string url = Request.Url.AbsolutePath;
    string updatedQueryString = "?" + nameValues.ToString();
    return url + updatedQueryString;
}

and then us it as follows 

Response.Redirect(ModifyQueryStringValue("SortBy","4"));

Upvotes: 2

Mathias Nohall
Mathias Nohall

Reputation: 757

    private void UpdateQueryString(string queryString, string value)
    {
        PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
        isreadonly.SetValue(this.Request.QueryString, false, null);
        this.Request.QueryString.Set(queryString, value);
        isreadonly.SetValue(this.Request.QueryString, true, null);
    }

Upvotes: 10

SkonJeet
SkonJeet

Reputation: 4905

The query string is passed TO the server. You can deal with the query string as a string all you like - but it won't do anything until the page is ready to read it again (i.e. sent back to the server). So if you're asking how to deal with the value of a query string you just simply access it Request.QueryString["key"]. If you're wanting this 'change' in query string to be considered by the server you just need to effectively reload the page with the new value. So construct the url again page.aspx?id=30 for example, and pass this into a redirect method.

Upvotes: 0

m.othman
m.othman

Reputation: 638

Retrieve the querystring of sortby, then perform string replace on the full Url as follow:

string sUrl = *retrieve the required complete url*
string sCurrentValue = Request.QueryString["sortby"];
sUrl = sUrl.Replace("&sortby=" + sCurrentValue, "&sortby=" + newvalue);

Let me know how it goes :)

Good luck

Upvotes: 10

Imran Rizvi
Imran Rizvi

Reputation: 7438

If you really want this you need to redirect to new same page with changed query string as already people answered. This will again load your page,loading page again just for changing querystring that is not good practice.

But Why do you need this?

If you want to change the value of sortBy from 6 to 4 to use everywhere in the application, my suggession is to store the value of query string into some variable or view state and use that view state everywhere.

For e.g.

in Page_Load you can write

if (!IsPostBack)
{
  ViewState["SortBy"] = Request.QueryString["sortBy"];
}

and everywhere else ( even after postback ) you can use ViewState["SortBy"]

Upvotes: 2

legrandviking
legrandviking

Reputation: 2414

I think you could perform a replacement of the query string in the following fashion on your server side code.

NameValueCollection filtered = new NameValueCollection(request.QueryString);

filtered.Remove("SortBy");
filtered.Add("SortBy","4");

Upvotes: 0

Massimiliano Peluso
Massimiliano Peluso

Reputation: 26727

The only way you have to change the QueryString is to redirect to the same page with the new QueryString:

Response.Redirect("YourPage.aspx?&sortBy=4")

http://msdn.microsoft.com/en-us/library/a8wa7sdt(v=vs.100).aspx

Upvotes: 0

James Hull
James Hull

Reputation: 3689

SolrNet has some very helpful Url extension methods. http://code.google.com/p/solrnet/source/browse/trunk/SampleSolrApp/Helpers/UrlHelperExtensions.cs?r=512

    /// <summary>
    /// Sets/changes an url's query string parameter.
    /// </summary>
    /// <param name="helper"></param>
    /// <param name="url">URL to process</param>
    /// <param name="key">Query string parameter key to set/change</param>
    /// <param name="value">Query string parameter value</param>
    /// <returns>Resulting URL</returns>
    public static string SetParameter(this UrlHelper helper, string url, string key, string value) {
        return helper.SetParameters(url, new Dictionary<string, object> {
            {key, value}
        });
    }

Upvotes: 0

Strillo
Strillo

Reputation: 2972

You can do it clientside with some javascript to build the query string and redirect the page using windows.open.

Otherwise you can use Response.Redirect or Server.Transfer on the server-side.

Upvotes: 0

Stilgar
Stilgar

Reputation: 23551

You need to redirect to a new URL. If you need to do some work on the server before redirecting there you need to use Response.Redirect(...) in your code. If you do not need to do work on the server just use HyperLink and render it in advance.

If you are asking about constructing the actual URL I am not aware of any built-in functions that can do the job. You can use constants for your Paths and QueryString arguments to avoid repeating them all over your code.

The UriBuilder can help you building the URL but not the query string

Upvotes: 0

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