Programatically using a string as object name when

问题:

This is a contrived example, but lets say I have declared objects:

CustomObj fooObj;
CustomObj barObj;
CustomObj bazObj;

And I have an string array:

string[] stringarray = new string[] {"foo","bar","baz"};

How can I programatically access and instantiate those objects using the string array, iterating using something like a foreach:

foreach (string i in stringarray) {
    `i`Obj = new CustomObj(i);
}

Hope the idea I'm trying to get across is clear. Is this possible in C#?

Thanks in advance.

回答1:

You need to be clear in your mind about the difference between an object and a variable. Objects themselves don't have names. Variable names are decided at compile-time. You can't access variables via an execution-time-determined name except via reflection.

It sounds like you really just want a Dictionary<string, CustomObj>:

Dictionary<string, CustomObj> map = new Dictionary<string, CustomObj>();

foreach (string name in stringArray)
{
    map[name] = new CustomObj(name);
}

You can then access the objects using the indexer to the dictionary.

If you're really trying to set the values of variables based on their name at execution time, you'll have to use reflection (see Type.GetField). Note that this won't work for local variables.

回答2:

You can't.

You can place them into a dictionary:

Dictionary<String, CustomObj> objs = new Dictionary<String, CustomObj>();

foreach (string i in stringarray)
{
    objs[i] = new CustomObj(i);
}

But that's about as good as it gets.

If you store the objects in fields in your class, like this:

public class SomeClass
{
    private CustomObj fooObj;
    private CustomObj barObj;
    private CustomObj bazObj;
}

Then you can reach them through reflection. Let me know if that's the route you want to take.

回答3:

you can use a find function:

    public static Control FindControl(string controlId, Control container)
    {
        if (container.ID == controlId)
            return container;

        foreach (Control control in container.Controls)
        {
            Control c = FindControl(controlId, control);
            if (c != null)
                return c;
        }
        return null;
    }

and then you will get your control, based on index like this: TextBox firstname = (TextBox) FindControl(string.Concat("TextBox", index.ToString()), this); I hope this helps.

回答4:

use this.Controls.Find(control_name,true)[0]...just remember to cast it

回答5:

This is possible using reflection if the variables are class member variables, but it's hideously slow for anything more than very specialized applications. I think if you detail what you're trying to do, we can better offer suggestions. There's very rarely a case where you should access a variable like you're doing.

回答6:

One option is the totally dynamic route, as per this article, where you specify a code block in a string and then compile/run it from within your program

回答7:

Another option, less flexible, but simpler is via Activator.CreateInstance - where you ask for a new object to be created - it won't assign to dynamic variables, but is that needed?

回答8:

@jotte: Thanks alot for that function. I used it and it works! Except that you need to change container.ID by container.Name

Then you just need to use something like (this example is for checkbox, but any type of variable could work):

string Test = "cbACn" + i.ToString(); CheckBox cbTest = (CheckBox)FindControl(Test, gbACSCAT); if (cbTest != null) { cbTest.Checked = true; }