Question

I would like to better understand the issue of setting new parameters to a url
and retrieve it via

var ParaValue = Request.QueryString["parameterName"];

so if I have a URL : “http://www.myWebsite.aspx?UserName=Alice”

I will retrieve it via example above

string uName = Request.QueryString["UserName"].ToString();

but what if I want to alter value e.g. make UserName = “Ralf”

• Re Edit

when a button is pressed ,
there is a parameter “state” that holds a reference to wich button was pressed
the value of state was = “none”
now i want to set it to img_button1.

i am not even sending the actuall imgbutton id

i am hard coding it just for testing /referencing

so i could know i am in the stage of event reaquested by the procidure of the given event of
button1

when event triggerd by img_button2

i whould then want to set the state to “img_button2”
etc’

Answer 1

after I have made my research (I couldn’t mark any answer kindly given here on my post)
then I tested two options I’ve encountered in this Stack Overflow Page:

first option (given by Ahmad Mageed) I have tested to work just fine .
and readability was easy to understand (as I am still fresh to asp.net ‘tricks’)

then followed the answer by
annakata which was remarkably improved approach in the way that you
don’t actually have to redirect to achieve result – Query String IS modified

after playing around i have desided to follow annakatas approach
and make a helper method that was using also a redirerion option
with modified QueryString Parameters & values.

public void QuerStrModify(string CurrQS_ParamName, string NewQs_paramName, string NewPar_Value, bool redirectWithNewQuerySettings = false)
{

    // reflect to readonly property 
    PropertyInfo isReadOnly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);

    // make collection editable 
    isReadOnly.SetValue(this.Request.QueryString, false, null);

    // remove 
    this.Request.QueryString.Remove(CurrQS_ParamName);

    // modify 
    this.Request.QueryString.Set(NewQs_paramName, NewPar_Value);

    // make collection readonly again 
    isReadOnly.SetValue(this.Request.QueryString, true, null);
    string FullUrl = Request.Url.AbsolutePath;
    if (redirectWithNewQuerySettings)
    {
        Response.Redirect(string.Join("?", FullUrl, this.Request.QueryString));
    }

}

i find it very helpful to someone that has Considerably less experience with asp.net developmet
so i posted it as my version of correct answer , as i see it .
i hope it’ll help somoeone else that seeks the same Solution.

feel free to further improve it , as i mentiond I’m not a proven talent ..yet.