Entity framework query not working using asp.net

Question

My entity framework query is not returning any value. I wanted to replicate this query through entity framework: SELECT name FROM guitarBrands WHERE image = image. So I ended up trying this code below.

public static string GetBrandByImage(string imageType)
{
    BrandsDBEntities obj = new BrandsDBEntities();

    string name = (from g in obj.guitarBrands where g.image == imageType select g.name).ToString();

    return name;
}

I'm really new at using entity framework and i really hope you guys can provide solutions for this.

A few things: Please provide more info, especially what exactly is returned from your query. Is it null? Is it an empty string? Secondly, have you tried the same query with LINQ? (string name = (obj.Set<guitarBrands>().Where(g => g.image == imageType).Select( g => g.name).ToString();Thirdly, you should always use using with contexts: using( var obj = new BrandsDBEntities() ) { ... }. Finally, what version of EF are you using? — Sentry
– Sentry, Commented Jun 17, 2017 at 11:43

Sentry · Accepted Answer · 2017-06-17 14:53:27Z

2

(from g in obj.guitarBrands where g.image == imageType select g.name)

return a list like an SQL query

To get the first element

(from g in obj.guitarBrands where g.image == imageType select g.name).First().Tostring();

or equivalent

obj.guitarBrands.Where(g => g.image == imageType).First().name;

edited Jun 17, 2017 at 14:53

Sentry

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answered Jun 17, 2017 at 11:50

Xilmiki

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1 Comment

Nkosi Over a year ago

Do mention that if there are no matches and First is called you would get an exception.

Nkosi · Accepted Answer · 2017-06-17 11:52:19Z

1

You are calling ToString on the query itself. Query needs to be enumerated first

public static string GetBrandByImage(string imageType) {
    using(var obj = new BrandsDBEntities()) {    
        var name = (from g in obj.guitarBrands 
                    where g.image == imageType 
                    select g.name).FirstOrDefault();

        return name;
    }
}

Using FirstOrDefault on the query as is would return the first name from any guitar brand that matches the predicate or null if no matches are found.

answered Jun 17, 2017 at 11:52

Nkosi

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