更新SQL数据源中的查询参数

Question

I have following code that updates the value of query parameters of a SQL Data Source after going through some conditions.

SqlDataSource sdm = new SqlDataSource("<our connection string>", "SELECT  [Message Id] ,[To] ,[From] ,[Reply To] ,[Subject] ,[Message] ,[Date added] FROM [database].[dbo].[User Messages] where ([to]=@sid or [from]=@sid) and ([to]=@qid or [from]=@qid)  and [reply to]=@rid");

string user = Session["USERID"].ToString();
string to = Request["to"].ToString();
string from = Request["from"].ToString();
sdm.UpdateParameters["rid"].DefaultValue = Request["replyid"].ToString();
sdm.UpdateParameters["sid"].DefaultValue = user;
if (user == to)
  sdm.UpdateParameters["qid"].DefaultValue=from;
else
  sdm.UpdateParameters["qid"].DefaultValue= to;

sdm.Update();
sdm.DataBind();
Repeater1.DataSource = sdm;
Repeater1.DataBind();

Its showing NullReferenceException at sdm.UpdateParameters["rid"].DefaultValue = Request["replyid"].ToString();

rid is already set in query string as ?rid=a

Answer 1

You'll want to use the Request.QueryString collection to get your rid parameter out:

sdm.UpdateParameters["rid"].DefaultValue = Request.QueryString["rid"];

Using an indexer with Request will get you values out of the QueryString , Form , Cookies or ServerVariables collections, using Request.QueryString directly makes your intentions that little bit clearer.

Answer 2

Shouldn't the query string be ?replyid=a instead of ?rid=a? .

It seems that Request["replyid"] returns null, and then ToString() throws the exception.