How to return linq to sql query result in web service asp.net?

Question

I'm beginner in web service and want to write simple query with LINQ to SQL and return that query result with Web Service,write this code:

[WebMethod]
public  string LinqExample()
{
    string conn = "Data Source=REMOVETHIS";
    DataClasses1DataContext behzad = new DataClasses1DataContext(conn);
    string result;
    var query = (from p in behzad.CDRTABLEs
                 where p.name == "behzad".Trim()
                 select p).Take(1);

    return query.ToString();
}

But when I run that web service,I get this error:

How can I solve that?

@user2946329 yes,i change that connection string and work it. — user3671271
– user3671271, Commented Jan 25, 2016 at 7:06

Markus Weninger · Accepted Answer · 2016-01-25 07:10:59Z

1

Three things:

1.) It seems your connection string is wrong, because there is a problem establishing the connection, not executing the query.

2.) You should not use Take(1), which returns an IEnumerable, but FirstOrDefault. You use Take if you want to take the first n elements, but First or FirstOrDefault if you only want exactly one result element.

3.) If using FirstOrDefault so, you have to do a null-check on returning: return query == null ? "" : query.ToString()

answered Jan 25, 2016 at 7:10

Markus Weninger

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