Unable to pass multiple values in querystring in .aspx to report at runtime

Hello Friends..

This should be simple process but now it became annoying issue.

I am trying to pass multiple value in query string in my ASP.Net web report in VS2012. The page has to pass multiple values to the report as a parameter . When I sent a single value (for eg: abc,) the data is being pulled up correctly but however when I am passing multiple values separated by a comma (eg abc,xyz) it is not displaying the results These multiple values separated by a comma are being passed to the page as query strings and we then are reading them and passing it to the report.

Please note:

For the parameter in the report, I set the default list of values and I also defined available set of values. Now when I am trying to trying pass the values to this parameter from c# code, it is still not accepting the values that I supplied instead it is taking all the values from available list. I think the problem is that the SSRS is not accepting values separated by a comma when "Allow multiple values" check box is checked. Please advise.

This is what I am trying so far:

ReportParameter pb1 = new ReportParameter();
try
{
string[] multiple;
string value = "";

if (!string.IsNullOrEmpty(Request.QueryString["pb1"]))
{
pb1.Name = "ProductBusiness1";
string[] strPb1 = Server.UrlDecode(Request.QueryString["pb1"]).Split(',');
value = Server.UrlDecode(Request.QueryString["pb1"]);

if (strPb1.Length > 0)
{
int i = 0;
value = "";
while (i < strPb1.Length)
{

if (value == string.Empty)
{
value = "'" + strPb1[i] + "'";
}
else
{
value += ", '" + strPb1[i] + "'";
}

i += 1;
}
}
multiple = new string[] { value };
//pb1.Values.Clear();
//pb1.Values.Add(value);
//string[] values = new string[] { Server.UrlDecode(Request.QueryString["pb1"]).ToString() };
//pb1.Values.AddRange(values);
//rptParams.Add(pb1);


pb1.Values.AddRange(multiple);
//Response.Write(value);
}

ReportParameter pb2 = new ReportParameter();
if (!string.IsNullOrEmpty(Request.QueryString["pb2"]))
{
pb2.Name = "ProductBusiness2";
pb2.Values.Add(Server.UrlDecode(Request.QueryString["pb2"]));
}

//hiddenResetCache
ReportParameter vt = new ReportParameter();
vt.Name = "ViewType";

string val = string.Empty;
if (hiddenResetCache.Text == "1")
{
hiddenResetCache.Text = "0";
val = returnCacheValue(true);
}
else
{
val = returnCacheValue(false);
}
vt.Values.Add(val);



ReportViewer1.ServerReport.SetParameters(new ReportParameter[] { plant });
if (!string.IsNullOrEmpty(pb1.Name))
{
ReportViewer1.ServerReport.SetParameters(new ReportParameter[] { pb1 });
}

if (!string.IsNullOrEmpty(pb2.Name))
{
ReportViewer1.ServerReport.SetParameters(new ReportParameter[] { pb2 });
}

ReportViewer1.ServerReport.SetParameters(new ReportParameter[] { vt });
}
catch (Exception ex)

I am aware that an alternative to using a comma delimited parameter is reusing the same parameter like: www.test.com/?pm1=test1&pm1=test2&pm1=test3. But this approach is not acceptable by the business and would like to have ability to separate values by coma itself. 

Please help, thanks much in advance