4

I have rewritten this question because not everyone understood. Hope it's ok, it's the same main problem.Very sorry

I have a winform with 15 progress bars called: "baraClasa1", "baraClasa2", "baraClasa3" ... "baraClasa15". I have to assign the .VALUE property (as in int) to all of them, from some database records. (The records access the different values from different time periods) I was thinking that maybe it is possible to use a loop to assign the .Value property to all of them by doing something like:

for(int i=0; i<value; i++)
{
   "baraClasa+i".Value = 20 + i;  
}

Is it possible to compose the name of the variables like that?

I don't know much about dictionaries, lists but looking into. If nothing works il just do the ugly:

int value = 20;
baraClasa1 = value;
baraClasa2 = value +1;....

Thank you for all help

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8
  • I don't think c# can do dynamic variable creation, your best bet is to use maybe collections or arrays. Commented Jan 3, 2014 at 16:39
  • Unless variable is, in fact, an array or other indexed collection, then [] is meaningless. Commented Jan 3, 2014 at 16:39
  • 1
    Rethink your design. An array is the way to go. Variable names are entirely for giving the developer a hint on what the purpose of the variable is. The program logic should not depend on variable names. Commented Jan 3, 2014 at 16:40
  • A dictionary would get you close to the same result. Calling an element would be dict["variableName"] msdn.microsoft.com/en-us/library/xfhwa508(v=vs.110).aspx Commented Jan 3, 2014 at 16:43
  • @FelixCastor: While being aware that "variableName" in that case is not actually (at least not automatically) a variable name. Commented Jan 3, 2014 at 16:45

8 Answers 8

Reset to default
5

You have to do a little reflection.

    public string variable0, variable1, variable2, variable3, variable4, variable5;

    private void button1_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < 6; i++)
        {
            //pretending my variable names are variable1, variable2.. ("variable" is NOT an array! just the "assign" variable)
            System.Reflection.FieldInfo info = this.GetType().GetField("variable" + i.ToString());

            // replace "testing" with the value you want e.g. assign[i]
            info.SetValue(this, "testing");
        }

        // Do something with your new values
    }

No need to use reflection with the updated question. The control collection has a built in find for getting a control by the name string.

 for (int i = 0; i < 6; i++)
 {
   ProgressBar bar = (ProgressBar)this.Controls["baraClasa" + i.ToString()];
   bar.Value =  50;
 }
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7 Comments

Performance and otherwise considerations aside, this will work only for fields, not for local variables.
Correct. His last edit said they are control names so this will do the trick. I agree that a redesign would be a better approach but sometimes that is not an option.
I believe that in this example I can only change the .Text property of the control?
Actually with your updated question you don't even have to use reflection. You can just find them by the string value in the control collection. I'll update my answer.
I will check into this later today and let you know how it went
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4

This is a design problem. Create a collection for items with common use (like progress bars for that matter) and iterate over the collection to perform actions on them.

If these are prorgress bars you might want to use an event-driven design (another link) to update their progress, meaning that each time a bar has made some progress, the event for the progress will send an update only to that bar, and not iterate over the entire list.

You may want to read an introduction to event driven programming in C# before re-factoring your code.

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2 Comments

Values are taken from a database from previous days, depending on the hour selected.. There isn't much event-driven design that I can think of
Still, you should be creating a collection to perform the operations as batch (you're right, event driven design is not necessary given your case). You can re-use the collection on every selection, so you don't have to re-create it. If the collection is found out to be different every time, then event-driven design may still apply after all.
3

It really isn't possible in C# to refer to local variables in a dynamic fashion as you are trying to do. Instead what you would do in C# is store the value in a dictionary where the key can be generated in a dynamic fashion.

For example let's say all of your variable1, variable2, ... variableN were of type int. Instead of 

int variable1 = 0;
int variable2 = 0;
...
int variableN = 0;

You would instead do the following

Dictionary<string, int> map = new Dictionary<string, int>();
for (int i = 0;  i < N; i++) {
  map[i.ToString()] = 0;
}

If the values are a of a fixed number and always linear in progress it may make sense to use an array instead of a dictionary

int[] array = new int[N];
for (int i = 0; i < N; i++) {
  array[i] = 0;
}
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Comments

2

You can't do it that way. You need an array. Every time you notice yourself having a variable2, you need an array. You may not know it yet, but you do.

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2

No, you can't do it in C#, it's syntactically impossible. But if you want access form controls which has different names like this you can do the following:

for(int i=0; i<20; i++)
{
  var name = "variable" + i;
  this.Controls[name].Text = "etc..." // here you can access your control
}
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9 Comments

it's syntactically impossible It most certainly is not. It's difficult, and almost always a bad idea, but it's most certainly not impossible. You could do it through reflection if the variables are instance fields, you could create an expression tree to handle most cases, and if worst comes to worst, you can always use unsafe to do...pretty much anything.
@Servy, really? You think it's possible with reflection? I don't know how to do this with reflection
It would depend on the specifics. I'm not sure if you could mutate a local with reflection. You can easily access the current instances (or any instances) fields by a string name though.
@Servy yeah maybe you right, we can create variable names dynamically and then access fields of current assembly in runtime.Actually it worth a try :D
As I said, it's almost certainly not the proper approach to this problem, and I would consider an answer along those lines to be actively harmful, however it is incorrect to say that doing so is impossible, because it most certainly is not, it's just undesirable.
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1

If you want to have names for your objects, use a dictionary:

Dictionary<string, type> myDict = new Dictionary<string, type>()
string naming = "MyPattern{0}";
for (int i = 0; i <value; i++) {
    myDict.add(string.Format(naming, i.ToString()), assign[i]);
}

And then you can access them by doing, for example:

myDict["MyPattern1"]

However, I suggest you would be better off using a collection like a List or array.

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Comments

1

Arrays, lists, dictionaries, hash maps... collections in general are what you would use here. For example, if you have a dictionary, then it consists of key/value pairs. So a dictionary might look like this:

var variable = new Dictionary<int, string>();

Where the int is the key for any given entry, and the string is the value. You'd assign values in something like this:

for(int i = 0; i < value; i++)
    variable.Add(i, assign[i]);

Of course, since i is just an incrementing integer in this case (unless you have some other key in mind?), then it works just as well as an indexer on a list. Something like this:

var variable = new List<string>();
for (int i = 0; i < value; i++)
    variable.Add(assign[i]);

In both cases, you'd access the assigned value later by referencing its key (in a dictionary) or its index (in a list, or any array):

var someOtherVariable = variable[x];

Where x is an integer value present in the dictionary's keys or in the array's size.

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0

If you can put names of all variables in an array such as 'variable', and they are unique, you can try to use dictionary :

    Dictionary<object, object> dictionary = new Dictionary<string, object>();
    for(int i=0; i<value; i++)
    {
         dictionary.Add(variable[i], assign[i]);
    }
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