Speed up Linq to Sql with compiled queries [duplic

问题:

This question already has an answer here:

• The query results cannot be enumerated more than once 2 answers

I have applied linq to sql in my project and it's taking a lot of time so I made a search to make it speedy and i have searched and took a reference from here

And my .cs code is

public static Func<DataClassesDataContext, int, IQueryable<editor_j_inf>>
editordetail1 = CompiledQuery.Compile((DataClassesDataContext db, int a) =>
                 from p1 in db.editor_j_infs
                 where p1.ed_journal_id == a
                 orderby p1.editor_id descending
                 select p1);   //Its my precompile process

public void editordetail()
{
    DataClassesDataContext db = new DataClassesDataContext();
    var rr = editordetail1(db,Convert.ToInt32(Server.HtmlEncode(Request.Cookies["j_id"].Value)));
    if (rr.Count() != 0)
    {
        txt_jtitle.Text = rr.First().j_title;
        txtissn_p.Text = rr.First().issn_p;           
    }        
}

but the error is coming as

回答1:

Here the line:

editordetail1(db,Convert.ToInt32(Server.HtmlEncode(Request.Cookies["j_id"].Value)));

is possible returning an IEnumerable<T>. And when you call Count() in rr.Count() then you have enumerated your results.

That's why when you are calling First() below, you are trying to enumerate second time.

txt_jtitle.Text = rr.First().j_title;

Try converting your return value from function: editordetail1 to a List as:

var rr = editordetail1(db,Convert.ToInt32(Server.HtmlEncode(Request.Cookies["j_id"].Value)));
var rrList = rr.ToList();

And now use the Count property on List and then call First()

if (rrList.Count() != 0) // use the List rrList
    {
        txt_jtitle.Text = rr.First().j_title; 
        txtissn_p.Text = rr.First().issn_p;           
    } 

回答2:

you need to change the following lines:

var rr = editordetail1(db,Convert.ToInt32(Server.HtmlEncode(Request.Cookies["j_id"].Value)));
if (rr.Count() != 0)

to:

var rr = editordetail1.Invoke(db,Convert.ToInt32(Server.HtmlEncode(Request.Cookies["j_id"].Value))).FirstOrDefault();
if (rr != null)