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Same as the last time you posted this:
Re: How to get an Not Empty Instance back ? - C# Discussion Boards[^]
You've found the item with the highest value; you just need to print that value:
public static TheQFromDB CalculateMaxVal(IEnumerable<TheQFromDB> input)
{
TheQFromDB result = null;
foreach (var item in input)
{
if (result == null || item.SecondsDiff > result.SecondsDiff)
{
result = item;
}
}
Console.WriteLine(result?.SecondsDiff ?? double.MinValue);
return result;
}
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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public static TheQFromDB CalculateMaxVal(List<TheQFromDB> input)
{
TheQFromDB Q = new TheQFromDB();
double maxValue = double.MinValue;
foreach(var i in input)
{
if (i.SecondsDiff > maxValue)
maxValue = i.SecondsDiff;
}
Console.WriteLine(maxValue);
return Q;
in this Ex here i have a List from Type TheQFromDB and insaid (input) several properties one of them is SecondsDiff .. i want get the class TheQfromDB back but with this code iam getting an Empty instance which call here Q .
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Try:
public static TheQFromDB CalculateMaxVal(IEnumerable<TheQFromDB> input)
{
TheQFromDB result = null;
foreach (var item in input)
{
if (result == null || item.SecondsDiff > result.SecondsDiff)
{
result = item;
}
}
return result;
}
NB: If there are no items in the input sequence, this will return null. If you want it to return an empty instance instead, change the last line to:
return result ?? new TheQFromDB();
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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could someone explain with an Ex why and how should use out ?
what is the benefit to use it ?
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out is a keyword which says that a method parameter will be changed in the method, but that it is not given an initial value - so any value in the "outside world" will not be passed into the method, but the outside world variable will have the new value after the method returns.
When you pass a "normal" parameter, it is passed by value: a copy of the value in the variable is given to the method, and changes will not be reflected in the outside world:
private void DoIt(int x)
{
x = x * 2;
Console.WriteLine(x);
}
...
int x = 100;
Console.WriteLine(x);
DoIt(x);
Console.WriteLine(x);Will print
100
200
100 You can pass a value by reference, and the actual outside world value is used in the method:
private void DoIt(ref int x)
{
x = x * 2;
Console.WriteLine(x);
}
...
int x = 100;
Console.WriteLine(x);
DoIt(ref x);
Console.WriteLine(x);Will print
100
200
200 Or, you could give it as an out parameter:
private void DoIt(out int x)
{
x = x * 2;
Console.WriteLine(x);
}
...
int x = 100;
Console.WriteLine(out x);
DoIt(out x);
Console.WriteLine(x);And you will get compiler errors because x has no initial value inside the DoIt method.
So you change your code:
private void DoIt(out int x)
{
x = 200;
Console.WriteLine(x);
}
...
int x = 100;
Console.WriteLine(x);
DoIt(out x);
Console.WriteLine(x);Will print
100
200
200
It's not used that much, but it's a way to "return multiple values" from a method if you need to.
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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thanks alot for the answer . it helped me
since i am a new user here how can i vote for your answer as helped or top answer or something like this .
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If you want to, then open the answer and you will see a green and red arrowhead at the top left. Green is "Good", red is "Bad".
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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Hi all;
Imagine I have defined 3 variables as follow:
String x1="Hello";
String x27="Hi";
String x99="Hey";
Then later in the program code I want to access the content of them by making their name.
Int i=27;
Messagebox.show("x" + i.tosting());
"x" + i.tosting() = "New";
What's the correct code in C#? Any idea?
Thank you in advance.
Rara
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You can't do that for local variables. The variables names are thrown away when you compile your code, so there's no way to reference them at run-time.
For fields or properties, you could use reflection[^]. It won't be pretty, and it won't be fast, but it should work.
class Foo
{
private string x1 = "Hello";
private string x27 = "Hi";
private string x99 = "Hey";
public string GetValue(int i)
{
string name = "x" + i;
FieldInfo field = typeof(Foo).GetField(name, BindingFlags.Instance | BindingFlags.NonPublic);
if (field == null) throw new ArgumentException("Unknown index: " + i, nameof(i));
return (string)field.GetValue(this);
}
}
Alternatively, put your values into a Dictionary<TKey,TValue>[^]:
Dictionary<int, string> x = new Dictionary<int, string>
{
[1] = "Hello",
[27] = "Hi",
[99] = "Hey",
};
int i = 27;
string value = x[i];
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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The speed issue will only be a problem if he repeatedly calls the reflection code hundreds of times. Not sure if speed is really an issue here (in his example, he's only got three properties).
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That's a very poor idea - you can do it using reflection, (but not for local variables since they are stack based, not heap) but that's like using a sledgehammer to crack a nut! It'll work, but that's a load of effort to go to just to break a thin shell...
Instead, consider an array:
private string[] x = new string[100];
...
x[1] = "Hello";
x[27] = "Hi";
x[99] = "Hey";
...
MessageBox.Show(x[i]); It really is a much better solution.
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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You could use a Dictionary<string,string>
and do this:
Dictionary<string,string> myFields = new Dictionary<string,string>();
myFields.Add("x1", "Hello");
myFields.Add("x27", "Hi");
myFields.Add("x99", "Hey");and then access them like this:
MessageBox.Show(myFields["x1"]);
or even:
string x1 = "x1";
string x27 = "x27";
string x99 = "x99";
MessageBox.Show(myFields[x1]);
".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013
modified 25-Apr-19 15:40pm.
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Or even:
string x1 = nameof(x1);
string x27 = nameof(x27);
string x99 = nameof(x99);
Dictionary<string,string> myFields = new Dictionary<string,string>();
myFields.Add(x1, "Hello");
myFields.Add(x27, "Hi");
myFields.Add(x99, "Hey");
MessageBox.Show(myFields[x1]);
Because "magic strings" are evil. 
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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I forgot about nameof. I like that option.
".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013
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I'm working on an adventure game and looking for some tips about coding the use of doors in rooms. I've got objects in rooms working fine, but trying to work out how to code for doors. Would you code for the door being an object in a room, but then the object is effectively in two rooms?
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I'm assuming that this is more like a text adventure with pictures or a point and click type game.
Seems like you would just want treat the Room as an object with child objects. So the door that leads to Room B from From Room A would really only exist in Room A and the door in Room B that leads to Room A would be a different object. After all you are loading a new room when you leave one and go to the other.
If this is a 3D or 2D Iso type game then the labryinth would be one big room with smaller rooms inside and you just have to deal with the door allowing/blocking line of sight or fog of war.
Anyway, my thoughts, take it all with a grain of salt. 
Jack of all trades, master of none, though often times better than master of one.
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Hi It's a text adventure.
Thank You for your thoughts. As you mentioned, I too thought about creating a pair of objects for each door, and then putting them in their appropriate locations.I'll have a go with that method. Just wanted to see if this was a good way forward. Enjoying the codeproject site, lots of good programming ideas. Thanks for your reply - much appreciated.
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No, I'd make "doors" a different class of "location attribute" - a "Direction" in which the player can move. That way, walking through a door is just the same as walking along a corridor - it moves you from "room 12: kitchen" to "room 24: dining room" just as walking north along a corridor takes you from "corridor 1: south end" to "corridor 2: north end". The opposite direction in the "new" room take you back to the previous (normally but adventure games have exceptions to that sometimes).
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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Hi - Thanks for the reply. I've got a location and an exit attribute, but was struggling with how a door attribute might work.
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I assume that you can interact with objects in the room?
In that case I would probably move into the direction of: door is an object, interacting with it "hides it" or "shows it" (open/close). If you remove it you can move into the direction of the "open door" resulting in a location outside the room's boundaries, in which case you know you need to load another room. In case of the closed door, the object blocks your way.
Even better would be to add properties to objects for example: can walk over, or can walk through. A "barrel" is something you can't walk over, but a piece of paper you can. Other objects you can pickup, push, look at, use, ...
makes sense?
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Hi - Yes, I've been using these ideas, and it works very will. For example get the object, only works if its getable property is true. Openable = True etc.
But Doors I'm thinking are a bit different as they are effectively in two locations. When you open the door in one location, the door in the adjacent location also opens.
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I can't find the article now but a few days ago this was posted from CP, I think. It is a github site where they published the source for all the old infocom games written in ZIL. The other link to Learning ZIL takes you to the book. On the right hand side you can get the book in a PDF form. The key takeaway is that chapter three explains the ZIL code for a room. You might find the logic behind the code interesting.
historicalsource[^]
Learning_ZIL_Steven_Eric_Meretzky_1995[^]
Jack of all trades, master of none, though often times better than master of one.
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I would define "doors" as a Class with state
open, closed, locked, unlocked, visible, invisible
with access permissions:
can close, can open ... set by functions in the main game engine that evaluate current game/player state
In the context of the Room Class, you could have any number of doors.
I would keep a data structure that maps doors to the room they connect to.
There's a lot to think about: should there be a collection of all Doors; should Doors have references to both rooms they connect ?
Have fun !
«Where is the Life we have lost in living? Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information?» T. S. Elliot
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Hi - Thanks - Definitely lots to think about. Given me some ideas to start planning.
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