Extension methods

Guest User

Ive wrote a few Extension\Helper methods for converting data from a database into a business object of the same type.

For example I have AsId(); which converts\casts a string to an int.

However, when I come to bolt on one of my Extension methods I am unable to, I want AsId(); added like so

CustomerId = reader["CustomerId"].AsId();

But when I use try to access the method from intellisense it only gives me the common base types ie ToString() etc.

How can I get intellisense to pick up my set of Extension methods? ive seen it done before but cant work out how to do it...

5 Replies

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Vulpes14y ago
Accepted answer
As you know, extension methods are always members of a static class and the latter is usually placed in its own namespace.

A 'using' directive then needs to be added to bring the namespace into scope.

From your description, I would guess that the signature of the AsId() method looks like this:

public static int AsId(this string s)
{
// code
}

If so and it's in scope, then it should show up in intellisense as soon as you type a dot after ToString().

As reader["CustomerId"] returns an object it will certainly need to have ToString() applied to it before you can parse it to an int.
Vulpes14y ago
Yes, you could do that and then use the Convert.ToInt32 overload which takes an object as a parameter.

However, you'd need to wrap the call in a try/catch in case some object is passed in which can't be converted to an int.
Jignesh Trivedi14y ago
hi,

can we use

public static int AsId(this object s)
{
//our code.
}

because reader["CustomerId"] is object type.
correct me if i am wrong.
Guest User14y ago
Vulpes

Unfortunately adding the ToString().AsId() didnt work : (

the code example I am referencing shows it is possible like so

CustomerId = reader["CustomerId"].AsId();

By pressing the dot after ["CustomerId"] in the reference code works fine!? but in my code it doesnt.

Ive checked reference assemblies etc and everything is like for like...
Vulpes14y ago
Try:

CustomerId = reader["CustomerId"].ToString().AsId();