How can I have access to an arraylist

Schmullus

Hi there, I have the following problem: I want to add a variable 'myServerInfo' to an arraylist. This variable is of the datatyp 'ServerInfo' (public class). I can add this variable without any problems to the arraylist with the command: myServerArrayList.Add(myServerInfo); But how can I have access to this through the arraylist? If I type in the following commandline, Intellisense will not provide me the necessary information: Console.WriteLine(myServerArrayList[0].??? I thought I can type in: Console.WriteLine(myServerArrayList[0].strServerName); Console.WriteLine(myServerArrayList[0].strServerIP); Console.WriteLine(myServerArrayList[0].strServerNetMask); My complete code for this example is like: using System; using System.Collections.Generic; using System.Text; using System.Collections; namespace ConsoleApplication1 { public class ServerInfo { public string strServerName; public string strServerIP; public string strServerNetMask; } class Program { static void Main(string[] args) { ArrayList myServerArrayList = new ArrayList(); ServerInfo myServerInfo = new ServerInfo(); myServerInfo.strServerName = "Server 1"; myServerInfo.strServerIP = "192.168.0.1"; myServerInfo.strServerNetMask = "255.255.255.0"; // Add to ArrayList myServerArrayList.Add(myServerInfo); Console.WriteLine(myServerArrayList[0].??? } } } If anybody gives me a hint, I can go on with my project.:) Thanks in advance Erik

Guffa

What you get from the ArrayList is a reference to the type Object. You have to cast the reference to the actual data type: (ServerInfo)(myServerArrayList[0])

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ejuanpp

Since anything derived from object can be stored in your ArrayList, Intellisense does not "know" what kind of object is stored in the 0th position. You need to cast it before: ((ServerInfo)myServerArrayList[0]). ... or use something more appropriate than ArrayList. Try List<ServerInfo> :)

George L Jackson

You have to cast it since it returns an object: (myServerArrayList[0] as myServerInfo).strServerName

Schmullus

Hi, I tried MessageBox.Show((ServerInfo)(myServerArrayList[0]).strServerName); but it won't work:confused: 'Object has no definition for strServerName' Erik

Schmullus

This works perfect! Thanks a lot:-D

bes2005

Arrays store System.Object type. When you add a new object or an item of promotive type they will be upcasted to System.Object. This is the line inside ArrayList which adds the new item: public virtual int Add(object value); Use Code DEfinition Window in VS 2005 to see what's inside ArrayList class. In order to access properties you need to down cast the array item you want to acces like: Console.WriteLine(((ServerInfo)myServerArrayList[0]).PropertyName); You would have the same problem if you tried: ArrayList myList = new ArrayList(); int int1 = 1; myList.Add(int1); int int2 = 2; myList.Add(int2); int int3 = myList[0]; // oops error - cannot convert type 'object' to 'int' int int3 = (int)myList[0]; // this will do the trick Happy coding ...

Russell Jones

make sure you only have serverinfo in that arraylist though item as ServerInfo will return null if item is not a serverinfo, this will create a runtime error. If you can and you are using 2005 i would try to use one of the generic collection types Collection or List as someone else suggested later. That's more likely to show errors at compile time. HTH Russ

ejuanpp

In (ServerInfo)(myServerArrayList[0]).strServerName ... It won't if the cast is applied after having attempted to retrieve the strServerName in (myServerArrayList[0]) which is recognized as an object type instance.

Schmullus

Thanks a lot for this detailed information!!

Guffa

Add parentheses so that you access the property of the ServerInfo object, not the Object object. MessageBox.Show(((ServerInfo)(myServerArrayList[0])).strServerName);

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