initializing and accessing dictionary globally

Question

Hi All I am loading Dictionary object with some values and wanted to access it throughout my project how can I do that. Please see explained below. public class class1{ class2 cl2 = new class2(); cl2. loadDataFile(); } public class class3{ string str = ______________________; class2 cls2 = new class2(); cls2. getStrings(str); } public class class2{ protected Dictionary store = new Dictionary (); public void loadDataFile() { //logic to load data from file on certain //conditions and store it in ' store ' Dictionary object declared above. } public string getStrings(sring str) { //Here I will access elements of ' store '. //I get '0' element. How to get elements here. } } Thanks

Sam Hobbs · Answer

Rohit I am sorry but I do not understand your code. It would help if you were to explain what it should do. You could provide a sample showing how class1 class2 and class3 are supposed to be used but I would prefer that you simply specify (with words) how they are to be used. In the code you provided class2 has the loadDataFile and getStrings methods. So I assume that the store dictionary will be loaded using loadDataFile and then that data will be used by getStrings. Yet you are caling loadDataFile only in class1 and you are calling getStrings only in class3. Vulpes's original suggestion was to make the store dictionary static but I am not sure that is what you need. It will really help if you can explain what you need to do. My best guess is that there is something more that we need to understand that your sample code does not tell us. Perhaps a better solution would be to use derive class1 and class3 from class2 or something like that. Do you understand that? In your original code class1 and class3 have class2 in them. So here is a simple question; will there be only one store dictionary for the entire program?

Sam Hobbs · Answer

I think the part that Vulpes does not show is how to access the Dictionary from outside the Program class. F rom outside the Program class we would just use Program. store to use the store Dictionary. Therefore we can use as many forms as we want for showing the data including changes to the data. Now that I look closer at Vulpes's code I think I would not do it that way. I would not move the loadDataFile out; it is better for the object to know how to load and unload its data. I will do a sample later; I have work to do at the moment.

Sam Hobbs · Answer

Vulpes I would prefer to have had an opportunity to explain it myself. For one thing I really want to understand what part of what I said that was not understood. It would really help me to know that. If Rohit does not understand what static means then we can explain that. I certainly tried to be as clear as possible. I strongly disagree that code is the only form of communication. Programmers can communicate without sample code and programmers should be capable of doing that. I would have provided sample code if relevant but I really want to understand what part of what I said was not clear. Do you understand?

Vulpes · Answer

Here's a console example of what Sam's talking about. class2 is no longer needed and so has been removed : using System; using System.Collections.Generic; public class class1 { public class1() { Program.loadDataFile(); } } public class class3 { string str = ______________________; public class3() { string name = Program.getStrings(str); Console.WriteLine(name); } } static class Program { internal static Dictionary store = new Dictionary (); static void Main() { class1 cls1 = new class1(); class3 cls3 = new class3(); Console.ReadKey(); } internal static void loadDataFile() { //logic to load data from file on certain //conditions and store it in 'store' Dictionary //object declared above. //add a key/value pair for demonstration store.Add(0 rohit); } internal static string getStrings(string str) { //Here I will access elements of 'store'. //I get '0' element. How to get elements here. if(store.ContainsKey(0)) { return store[0]; } return null; } }

rohit pol · Answer

Thanks for reply. It will be great if you explain this by some example code.

Sam Hobbs · Answer

The Program class in the Program.cs file is a static class. That is a good place to put static instances of your classes; actually they are not called instances. You would want to make them static members. Do the loading part in the Program class before the mesage loop (Application.Run). If you do that then there is no need to make class1 calss2 or class3 static and there is no need to make any members of the static. Your Main in the Program class in the Program.cs file would do essentially what the main does in the Test class of Vulpes's code except you would not need the Test class (and not the Console.ReadKey of course). Do you understand or do you need sample code? You can ask questions to get clarification of what I mean if you need to.

Vulpes · Answer

If you want the same Dictionary object to be accessible by all instances of Class2 then you need to make it into a static rather than an instance field. Otherwise if you use one instance to load the data and another instance to get an element of the Dictionary then the second instance will be looking at an empty Dictionary as it won't be the same object as was populated by the first instance. using System; using System.Collections.Generic; public class class1{ class2 cl2 = new class2(); public class1() { cl2.loadDataFile(); } } public class class3{ string str = ______________________; class2 cls2 = new class2(); public class3() { string name = cls2.getStrings(str); Console.WriteLine(name); } } public class class2{ private static Dictionary store = new Dictionary (); public void loadDataFile() { //logic to load data from file on certain //conditions and store it in 'store' Dictionary //object declared above. //add a key/value pair for demonstration store.Add(0 rohit); } public string getStrings(string str) { //Here I will access elements of 'store'. //I get '0' element. How to get elements here. if(store.ContainsKey(0)) { return store[0]; } return null; } } class Test { static void Main() { class1 cls1 = new class1(); class3 cls3 = new class3(); Console.ReadKey(); } }