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How do I refresh an array full of returned values of method calls?

In C#, I have a string array that I have written full full of "getter" method calls. They call methods in another class so that the array is populated with the needed strings. It looks something like this:
string[] mCalls = {c.get1(), c.get2(), c.get3()};
I'm sure this situation could apply to any program. However, in my program the variables these methods return are initially set with the string "Unchecked" - thus filling this example array with Unchecked 3 times. As my program goes on and things are checked, the values of the string variables get changed within the class they're in. I've been simply re-calling the getter methods at appropriate times to change what's in my array, like this:
mCalls[0] = c.get1();
mCalls[1] = c.get2();
mCalls[2] = c.get3();
I don't really like this. It seems inevitable that one day I'll have to change something, and if that happens I will have to manually do the tedious work of changing all of the indexing throughout my program. If this happens to be the best way I'm fine with that, but I assume there are better ways. So, in any case, is there a way to "refresh" the values in an array that is set up like this? And if so, what is it?

You want something like this:
public string[] MCalls
{
get
{
return new string[]{c.get1(), c.get2(), c.get3()};
}
private set;
}
and then use MCalls as if it is a regular variable whenever you want to access the arrays

You could change your array to contain functions instead of strings like this:
Func<string>[] mCalls = { c.get1, c.get2, c.get3...};
And then use it this way:
string c2 = mCalls[1]();
But note that this way every access is a method call. I'm not sure what you are really trying to achieve, there may be better overall designs than this approach.

Couple of options:
Create an array of lambdas:
var mCalls = new Func<object, string>[] {
(object o) => o.ToString() ,
(object o) => o.GetHashCode().ToString(),
(object o) => o.GetType().ToString(),
};
If the input to each lambda is the same you can create a lambda that returns an array:
Func<object, string[]> GetValues = (object o) => new string[]
{
o.ToString() ,
o.GetHashCode().ToString(),
o.GetType().ToString(),
};
Then just reload the array by calling the lambda:
mCalls = GetValues(c);
Note that it isn't technically refreshing the array, it's creating a new array. If you need to keep the array the same but just update the values you'd ned to loop through the array and assign the values by index.

What you could do is loop thorugh with reflection and get all methods from the class and from here you can get a list of method names. With this list you can assign to an array or run the methods by name or whatever. You can also filter the list to get your specific method names only:
var methodNames = typeof(MyClass).GetMethods(BindingFlags.Public | BindingFlags.Static)
.Select(x => x.Name)
.Distinct()
.OrderBy(x => x);
To call the methods:
foreach(var method in methodNames)
{
typeof(MyClass).GetMethod(method).Invoke(t, new[] { "world" });
}

list property containing two types (string/int)

I need to have a property that will be an array that can hold both ints and strings.
if i set the property to an array of ints it should be ints so when I am searching through this array the search will be fast, and at odd times this property will also contain strings which the search will be slow.
Is there any other way other than the following to have a list that contain native types
two properties one for ints and one for strings
use List< object >
UPDATE:
The use-case is as follow. I have a database field [ReferenceNumber] that holds the values (integers and strings) and another field [SourceID] (used for other things) which can be used to determine if record holds an int or string.
I will be fetching collections of these records based on the source id, of course depending on what the source is, the list either will be integers or strings. Then I will go through this collection looking for certain reference numbers, if they exist not add them or they dont then add them. I will be pre-fetching a lot of records instead of hitting the database over and over.
so for example if i get a list for sourceid =1 that means they are ints and if searching i want the underline list to be int so the search will be fast. and if sourceid say is 2 which means they are strings and very rare its okay if the search is slow because those number of records are not that many and a performance hit on searching through strings is okay.

I will go through this collection looking for certain reference numbers, if they exist not add them or they dont then add them.
It sounds to me like you don't need a List<>, but rather a HashSet<>. Simply use a HashSet<object>, and Add() all the items, and the collection will ignore duplicate items. It will be super-fast, regardless of whether you're dealing with ints or strings.
On my computer, the following code shows that it takes about 50 milliseconds to populate an initial 400,000 unique strings in the hashset, and about 2 milliseconds to add an additional 10,000 random strings:
var sw = new Stopwatch();
var initial= Enumerable.Range(1, 400000).Select(i => i.ToString()).ToList();
sw.Start();
var set = new HashSet<object>(initial);
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);
var random = new Random();
var additional = Enumerable.Range(1, 10000).Select(i => random.Next(1000000).ToString()).ToList();
sw.Restart();
foreach (var item in additional)
{
set.Add(item);
}
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds);
Also, in case it's important, HashSet<>s do retain order of insertion.

The only other thing I would suggest is a custom object that implements IComparable
class Multitype: IComparable
{
public int? Number { get; set; }
public string Words {get; set; }
public int CompareTo(object obj)
{
Multitype other = obj as Multitype;
if (Number != null && other != null && other.Number != null)
{
//...
}
else
{
//...
}
}
}
There will be some extra comparison steps between numbers, but not as much as string parsing.
Are you storing a ton of data, is that performance difference really going to matter?

It's possible to use generics if you implement them on the class. Not sure if this solves your problem. Would be interested to hear the real-world example of a property that can have different types.
class Foo<T>
{
public List<T> GenericList { get; set; }
public Foo()
{
this.GenericList = new List<T>();
}
}

If by "use List" you mean the object primitive or provided System.Object, that is an option, but I think it would behoove you to make your own wrapper object -- IntString or similar -- that would handle everything for you. It should implement IComparable, as the other gal mentioned.
You can increase the efficiency of sorting your object in collections by writing a CompareTo method that does exactly what you need it to. Writing a good CompareTo method is a whole can of worms in itself, so you should probably start a new question for that, if that's what you want.
If you're looking for a property that is strongly typed as a List<Int> or List<String> at instantiation, but can change afterwards, then you want an interface. IList exists, but won't help you, since that must also be strongly typed upon declaration. You should probably make something like IIntStringList that can only be one of List<Int> or List<String>.
Sorry this answer doesn't have that many details (I need to leave the office now), but I hope I've set you on the right track.

Store variables in list/array and loop through later c#

Sorry, I think I was not clear earlier. I am trying to do as O.R.mapper says below- create a list of arbitrary variables and then get their values later in foreach loop.
Moreover, all variables are of string type so I think can come in one list. Thanks.
Is there a way to store variables in a list or array then then loop through them later.
For example: I have three variables in a class c named x,y and Z.
can I do something like:
public List Max_One = new List {c.x,c.y,c.z}
and then later in the code
foreach (string var in Max_One)
{
if ((var < 0) | (var > 1 ))
{
// some code here
}
}

Is there a particular reason why you want to store the list of variables beforehand? If it is sufficient to reuse such a list whenever you need it, I would opt for creating a property that returns an IEnumerable<string>:
public IEnumerable<string> Max_One {
get {
yield return c.x;
yield return c.y;
yield return c.z;
}
}
The values returned in this enumerable would be retrieved only when the property getter is invoked. Hence, the resulting enumerable would always contain the current values of c.x, c.y and c.z.
You can then iterate over these values with a foreach loop as alluded to by yourself in your question.
This might not be practical if you need to gradually assemble the list of variables; in that case, you might have to work with reflection. If this is really required, please let me know; I can provide an example for that, but it will become more verbose and complex.

Yes, e.g. if they are all strings:
public List<string> Max_One = new List<string> {c.x,c.y,c.z};
This uses the collection initializer syntax.
It doesn't make sense to compare a string to an int, though. This is a valid example:
foreach (string var in Max_One)
{
if (string.IsNullOrEmpty(var))
{
// some code here
}
}

If your properties are numbers (int, for example) you can do this:
List<int> Max_One = new List<int> { c.x, c.y, c.Z };
and use your foreach like this
foreach(int myNum in Max_One) { ... } //you can't name an iterator 'var', it's a reserved word
Replace int in list declaration with the correct numeric type (double, decimal, etc.)

You could try using:
List<object> list = new List<object>
{
c.x,
c.y,
c.z
};

I will answer your question in reverse way
To start with , you cannot name your variable with "var" since it is reserved name. So what you can do for the foreach is
foreach (var x in Max_One)
{
if ((x< 0) || (x> 1 ))
{
// some code here
}
}
if you have .Net 3.0 and later framework, you can use "var" to define x as a member of Max_One list without worrying about the actual type of x. if you have older than the version 3.0 then you need to specify the datatype of x, and in this case your code is valid (still risky though)
The last point (which is the your first point)
public List Max_One = new List {c.x,c.y,c.z}
There are main thing you need to know , that is in order to store in a list , the members must be from the same datatype, so unless a , b , and c are from the same datatype you cannot store them in the same list EXCEPT if you defined the list to store elements of datatype "object".
If you used the "Object" method, you need to cast the elements into the original type such as:
var x = (int) Max_One[0];
You can read more about lists and other alternatives from this website
http://www.dotnetperls.com/collections
P.s. if this is a homework, then you should read more and learn more from video tutorials and books ;)

Clarification needed regarding basic indexer and collection in C#

I'm going through another developer's code, which is shown below:
[XmlElement("AdminRecipient")] public AdminRecipient[] AdminRecipientCollection = new AdminRecipient[0];
public AdminRecipient this[ string type ]
{
get
{
AdminRecipient result = null;
foreach( AdminRecipient emailRecipient in AdminRecipientCollection )
{
if( emailRecipient.Type == type )
{
result = emailRecipient;
break;
}
}
return( result );
}
Can someone explain what's going to happen in this line?
public AdminRecipient[] AdminRecipientCollection = new AdminRecipient[0];
The XML file that contains all of the email recipients has about 5 email addresses. But by using [0], will the foreach loop return each of those email addresses?
I have a basic understanding of indexers, but I don't this. What does it do?:
public AdminRecipient this[ string type ]
At the end of the day, the problem here is that the application doesn't send out an email when all 5 recipients are in the xml file. If I replace the 5 addresses with just 1 email addresses, then I'm able to get the email (which leads me to believe that there's a logic issue somewhere here).

An indexer allows you to use a type with the same syntax as array access. One of the simplest examples would be List<T>:
List<string> x = new List<string>();
x.Add("Item 0");
x.Add("Item 1");
string y = x[0]; // "Item 0"
That use of x[0] is calling the indexer for List<T>. Now for List<T> the index is an integer, as it is for an array, but it doesn't have to be. For example, with Dictionary<TKey, TValue> it's the key type:
Dictionary<string, string> dictionary = new Dictionary<string, string>();
dictionary.Add("foo", "bar");
string fetched = dictionary["foo"]; // fetched = "bar"
You can have a "setter" on an indexer too:
dictionary["a"] = "b";
Your indexer is just returning the first AdminRecipient in the array with a matching type - or null if no match can be found.
(It's unfortunate that the code you've shown is also using a public field, by the way. It would be better as a property - and probably not an array, either. But that's a separate discussion.)
EDIT: Regarding the first line you highlighted:
public AdminRecipient[] AdminRecipientCollection = new AdminRecipient[0];
That will create an array with no elements, and assign a reference to the AdminRecipientCollection field. With no further changes, the foreach loop would not have anything to iterate over, and the indexer will always return null.
However, presumably something else - such as XML serialization - is assigning a different value to that field - populating it with more useful data.

The line you're asking about is an assignment of AdminRecipientCollection to an empty array. This assignment will occur at instantiation time. The deserialization of the XML will happen after the class is instantiated, if ever. The author's purpose here is presumably to ensure that AdminRecipientCollection will never be null, even in case the class is used before XML is deserialized into it.
By ensuring that AdminRecipientCollection is never null, the author can ignore the possibility that the foreach loop will throw a NullReferenceException. At least, that's probably the hope.
Unfortunately, because AdminRecipientCollection is public, the AdminRecipient property could still throw, as in the following case:
var demoClass = new DemoClass();
demoClass.AdminRecipientCollection = null;
var firstRecipient = demoClass[0];
To prevent this possibility, remove the initial assignment and check for null in the AdminRecipient property before beginning the enumeration.

c# modifying structs in a List<T>

Short question: How can I modify individual items in a List? (or more precisely, members of a struct stored in a List?)
Full explanation:
First, the struct definitions used below:
public struct itemInfo
{
...(Strings, Chars, boring)...
public String nameStr;
...(you get the idea, nothing fancy)...
public String subNum; //BTW this is the element I'm trying to sort on
}
public struct slotInfo
{
public Char catID;
public String sortName;
public Bitmap mainIcon;
public IList<itemInfo> subItems;
}
public struct catInfo
{
public Char catID;
public String catDesc;
public IList<slotInfo> items;
public int numItems;
}
catInfo[] gAllCats = new catInfo[31];
gAllCats is populated on load, and so on down the line as the program runs.
The issue arises when I want to sort the itemInfo objects in the subItems array.
I'm using LINQ to do this (because there doesn't seem to be any other reasonable way to sort lists of a non-builtin type).
So here's what I have:
foreach (slotInfo sInf in gAllCats[c].items)
{
var sortedSubItems =
from itemInfo iInf in sInf.subItems
orderby iInf.subNum ascending
select iInf;
IList<itemInfo> sortedSubTemp = new List<itemInfo();
foreach (itemInfo iInf in sortedSubItems)
{
sortedSubTemp.Add(iInf);
}
sInf.subItems.Clear();
sInf.subItems = sortedSubTemp; // ERROR: see below
}
The error is, "Cannot modify members of 'sInf' because it is a 'foreach iteration variable'".
a, this restriction makes no sense; isn't that a primary use of the foreach construct?
b, (also out of spite) what does Clear() do if not modify the list? (BTW, the List does get cleared, according to the debugger, if I remove the last line and run it.)
So I tried to take a different approach, and see if it worked using a regular for loop. (Apparently, this is only allowable because gAllCats[c].items is actually an IList; I don't think it will allow you to index a regular List this way.)
for (int s = 0; s < gAllCats[c].items.Count; s++)
{
var sortedSubItems =
from itemInfo iInf in gAllCats[c].items[s].subItems
orderby iInf.subNum ascending
select iInf;
IList<itemInfo> sortedSubTemp = new List<itemInfo>();
foreach (itemInfo iInf in sortedSubItems)
{
sortedSubTemp.Add(iInf);
}
//NOTE: the following two lines were incorrect in the original post
gAllCats[c].items[s].subItems.Clear();
gAllCats[c].items[s].subItems = sortedSubTemp; // ERROR: see below
}
This time, the error is, "Cannot modify the return value of 'System.Collections.Generic.IList.this[int]' because it is not a variable." Ugh! What is it, if not a variable? and when did it become a 'return value'?
I know there has to be a 'correct' way to do this; I'm coming to this from a C background and I know I could do it in C (albeit with a good bit of manual memory management.)
I searched around, and it seems that ArrayList has gone out of fashion in favor of generic types (I'm using 3.0) and I can't use an array since the size needs to be dynamic.

Looking at the for-loop approach, the reason (and solution) for this is given in the documentation for the compilation error:
An attempt was made to modify a value
type that is produced as the result of
an intermediate expression but is not
stored in a variable. This error can
occur when you attempt to directly
modify a struct in a generic
collection.
To modify the struct, first assign it
to a local variable, modify the
variable, then assign the variable
back to the item in the collection.
So, in your for-loop, change the following lines:
catSlots[s].subItems.Clear();
catSlots[s].subItems = sortedSubTemp; // ERROR: see below
...into:
slotInfo tempSlot = gAllCats[0].items[s];
tempSlot.subItems = sortedSubTemp;
gAllCats[0].items[s] = tempSlot;
I removed the call to the Clear method, since I don't think it adds anything.

The problem you are having in your foreach is that structs are value types, and as a result, the loop iteration variable isn't actually a reference to the struct in the list, but rather a copy of the struct.
My guess would be the compiler is forbidding you change it because it most likely would not do what you expect it to anyway.
subItems.Clear() is less of a problem, because altho the field may be a copy of the element in the list, it is also a reference to the list (shallow copy).
The simplest solution would probably be to change from a struct to a class for this. Or use a completely different approach with a for (int ix = 0; ix < ...; ix++), etc.

The foreach loop doesn't work because sInf is a copy of the struct inside items. Changing sInf will not change the "actual" struct in the list.
Clear works because you aren't changing sInf, you are changing the list inside sInf, and Ilist<T> will always be a reference type.
The same thing happens when you use the indexing operator on IList<T> - it returns a copy instead of the actual struct. If the compiler did allow catSlots[s].subItems = sortedSubTemp;, you'll be modifying the subItems of the copy, not the actual struct. Now you see why the compiler says the return value is not a variable - the copy cannot be referenced again.
There is a rather simple fix - operate on the copy, and then overwrite the original struct with your copy.
for (int s = 0; s < gAllCats[c].items.Count; s++)
{
var sortedSubItems =
from itemInfo iInf in gAllCats[c].items[s].subItems
orderby iInf.subNum ascending
select iInf;
IList<itemInfo> sortedSubTemp = new List<itemInfo>();
foreach (itemInfo iInf in sortedSubItems)
{
sortedSubTemp.Add(iInf);
}
var temp = catSlots[s];
temp.subItems = sortedSubTemp;
catSlots[s] = temp;
}
Yes, this results in two copy operations, but that's the price you pay for value semantics.

The two errors you specified have to do with the fact that you are using structs, which in C# are value types, not reference types.
You absolutely can use reference types in foreach loops. If you change your structs to classes, you can simply do this:
foreach(var item in gAllCats[c].items)
{
item.subItems = item.subItems.OrderBy(x => x.subNum).ToList();
}
With structs this would need to change to:
for(int i=0; i< gAllCats[c].items.Count; i++)
{
var newitem = gAllCats[c].items[i];
newitem.subItems = newitem.subItems.OrderBy(x => x.subNum).ToList();
gAllCats[c].items[i] = newitem;
}
The other answers have better information on why structs work different than classes, but I thought I could help with the sorting part.

If subItems was changed to a concrete List instead of the interface IList, then you'd be able to use the Sort method.
public List<itemInfo> subItems;
So your whole loop becomes:
foreach (slotInfo sInf in gAllCats[c].items)
sInf.subItems.Sort();
This won't require the contents of the struct to be modified at all (generally a good thing). The struct's members will still point to exactly the same objects.
Also, there are very few good reasons to use struct in C#. The GC is very, very good, and you'd be better off with class until you've demonstrated a memory allocation bottleneck in a profiler.
Even more succinctly, if items in gAllCats[c].items is also a List, you can write:
gAllCats[c].items.ForEach(i => i.subItems.Sort());
Edit: you give up too easily! :)
Sort is very easy to customise. For example:
var simpsons = new[]
{
new {Name = "Homer", Age = 37},
new {Name = "Bart", Age = 10},
new {Name = "Marge", Age = 36},
new {Name = "Grandpa", Age = int.MaxValue},
new {Name = "Lisa", Age = 8}
}
.ToList();
simpsons.Sort((a, b) => a.Age - b.Age);
That sorts from youngest to oldest. (Isn't the type inference good in C# 3?)