CODEWITHSUNDEEP
c#asp.net.netentity-frameworklinq
crony
crony

Reputation: 511

The result of a query cannot be enumerated more than once.

I have a listview dialog to bind a data to that listview.

private void BindListView(string DCLookupMstr_Value, int reportCatId, string DCLookup_Value = null)

    {          

         using (Model.OperationalAnalyticsEntities oadb = new Model.OperationalAnalyticsEntities())
            {
                var res = oadb.prGetDailyCensusLookup(DCLookupMstr_Value, reportCatId, DCLookup_Value);
                Session["LookupValues"] = res;
                lvLookup.DataSource = res.ToList();
                lvLookup.DataBind();
            }            
    }

And I put a search box(textbox) on that listview dialog. If user type any text/chars, using linq query..populate the listview again with the values which contains given chars. My code is below

protected void txtSearch_TextChanged(object sender, EventArgs e)
    {
        var text = txtSearch.Text;
        //var list = new List<Model.prGetDailyCensusLookup_Result>();
        var lookUpValue = Session["LookupValues"] as ObjectResult<Model.prGetDailyCensusLookup_Result>;
        var list = lookUpValue.Where(x => x.DCLookup_Value.Contains(text));

        lvLookup.DataSource = list.ToList();
        lvLookup.DataBind();  
     }

I am getting the "result of a query cannot be enumerated more than once" where ever i added .ToList(). I am not sure what did I miss.

Please Help!

Upvotes: 0

Views: 2186

Answers (2)

David Culp
David Culp

Reputation: 5480

You value you are storing in Session is the LINQ query, not the result of the query. The second time it is used (the list.ToList()) it throws this error.

This is easily fixed by storing the result as a list in Session instead.

var res = oadb.prGetDailyCensusLookup(DCLookupMstr_Value, reportCatId, DCLookup_Value)
              .ToList();
Session["LookupValues"] = res;
lvLookup.DataSource = res;
lvLookup.DataBind();

Upvotes: 0

Thomas Levesque
Thomas Levesque

Reputation: 292425

In BindListView, when you do .ToList(), it enumerates the query for the first time. And what you store in the session is the query itself. When you do .ToList() again in txtSearch_TextChanged, it enumerates the query a second time, which is not supported.

You should store the result of .ToList() in the session, rather than the query:

Session["LookupValues"] = lvLookup.DataSource = res.ToList();

Upvotes: 2

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