This question already has an answer here:
Define variable type conditionally C#
(1 answer)
Closed 2 years ago.
I'm trying to declare a variable that is dependent on the bool 'multiline'.
<...some code...>
if (multiline)
{
string[] line;
}
else
{
string line;
}
<...code that uses 'line'...>
But this doesn't work because the declaration of the variables is at the wrong stack level (I think); these variables would only be able to be used within the if/else statements, but I would like to be able to use them outside of the if/else statements.
Is there a way in C# to conditionally create variables?
string[] str;
if (multiline)
{
string[] line = str;
}
else
{
string line = str[0];
}
The short answer is no.
However, I do not believe the question is explained well. Please rethink if you wish to declare a variable dynamically or use its value dynamically.
If the later is true, you can use it in below 2 ways.
Using dynamic
dynamic lines;
if (multiline)
{
lines = new string[10];
}
else
{
lines = "<some string value>";
}
Using array of strings.
string[] lines;
if (multiline)
{
lines = <<string array values>>
}
else
{
lines = "<some string value>";
}
if(lines.Length == 1)
{
// handle single line
}
if(lines.Length > 1)
{
// handle multi line
}
Understand that even if the variables are declared conditionally/dynamically you will have to determine the type at a later point when you wish to handle the variable. My advice would be to bring more details to this question for us to help you better.
Related
This question already has answers here:
Why did I get the compile error "Use of unassigned local variable"?
(10 answers)
What does "Use of unassigned local variable" mean?
(11 answers)
Closed 1 year ago.
Error: Use of unassigned local variable 'Datafiles'
I know this question is asked several times, but I don't see anything that suits my requirement. please help!
From the following code to check if files exists, I'm getting the following error, any suggestion on how to fix it, I've already included system.IO on top in namespaces
public void Main()
{
// TODO: Add your code here
string DataFilesLocation;
string[] DataFiles ;
DataFilesLocation = Dts.Variables["User::FolderPath"].Value.ToString();
if (DataFiles.Length > 0)
{
Dts.Variables["User::Flag"].Value = true;
}
Dts.TaskResult = (int)ScriptResults.Success;
}
Thanks fr your help in advance.
You need to assign both variables before you use them, and a best-practice in C# is to assign variables on the line you declare them, if you can.
So it should look something like:
string dataFilesLocation = Dts.Variables["User::FolderPath"].Value.ToString();
string[] dataFiles = System.IO.Directory.GetFiles(dataFilesLocation);
You never assign anything to DataFiles.
Try initializing it with an array size and populating those indexes, or assigning an array to it.
E.G
public void Main()
{
string DataFilesLocation;
// initializes your variable, removing the error you are getting
string[] DataFiles = new string[5];
//populates the array with file names
for(int i=0 ; i< 5 ; i++){
DataFiles[i]="FilePrefix"+i+".png";
}
DataFilesLocation = Dts.Variables["User::FolderPath"].Value.ToString();
if (DataFiles.Length > 0)
{
Dts.Variables["User::Flag"].Value = true;
}
Dts.TaskResult = (int)ScriptResults.Success;
}
This question already has answers here:
Access variable inside while loop from outside (C#)?
(4 answers)
how to use a variable outside of an if statement that is already declared inside an if statement
(2 answers)
Closed 2 years ago.
I am trying to assign a bool variable if it is true or false according to a if statement. But after that I want to use the same variable outside of the if statement for a different if statement and use it as a condition. Is there any way to interact with the bool created inside of an if statement also outside of the if statement? It is written in C#.
This is an example:
string enteredPassword = Console.ReadLine();
if (enteredPassword == "magic")
{
bool passwordIsValid = true;
}
else
{
bool passwordIsValid = false;
}
if (passwordIsValid)
{
Console.WriteLine("Access Granted!");
}
else
{
Console.WriteLine("Access Denied!");
}
I want to use variable passwordIsValid to determine if the if function should be triggered or moved on to else. Thanks
This question already has answers here:
Return multiple values to a method caller
(28 answers)
Closed 3 years ago.
I am trying to code a little console game but I have a little problem.
In order to not write a function for every single decision the player will make, I need to know if there is a possibility to return multiple values in a single function. Below is a little example on what I have at the moment.
public static string three_Days_before()
{
Console.Write("72 hours earlier...");
Console.WriteLine(); //Just a little space.
string first_sentence = "";
Console.WriteLine(); //Just a little space.
string second_sentence = "";
}
So here is what I have. And I want to know if I can somehow return both strings within the same function, without the need to write a function for every scene in order to be called in the Main() later.
As of C# 7 you can return a ValueTuple with the following syntax:
public static (string, string) three_Days_before()
{
Console.Write("72 hours earlier...");
Console.WriteLine(); //Just a little space.
string first_sentence = "";
Console.WriteLine(); //Just a little space.
string second_sentence = "";
return (first_sentence, second_sentence);
}
You can optionally give them names too, the underlying type remains the same, but consuming it can be a bit nice as each item can have a name.
public static (string first_sentence, string second_sentence) three_Days_before()
{
Console.Write("72 hours earlier...");
Console.WriteLine(); //Just a little space.
string first_sentence = "";
Console.WriteLine(); //Just a little space.
string second_sentence = "";
return (first_sentence, second_sentence);
}
This question already has answers here:
Simply check for multiple statements C#
(2 answers)
C# - Prettier way to compare one value against multiple values in a single line of code [duplicate]
(2 answers)
Closed 3 years ago.
I have got method:
private bool MyMethod(PlantType plantType)
{
return plantType.PlantMoveType == PlantMoveType.PlantReady
|| plantType.PlantMoveType == PlantMoveType.PlantRelase
}
Can I write it into other way? Maybe with LINQ?
One way is to put the enum values that you want to check against into an array, and call Contains.
return new[] { PlantMoveType.PlantReady, PlantMoveType.PlantRelase }
.Contains(plantType.PlantMoveType);
If you are using C# 7 or later, you can also write the method as expression-bodied:
private bool MyMethod(PlantType plantType) =>
new[] { PlantMoveType.PlantReady, PlantMoveType.PlantRelase }
.Contains(plantType.PlantMoveType);
Well a small simplification would be to pass the type (enum?) of the property PlantMoveType instead of PlantType as the parameter.
Beyond that, you could declare the types to check for as e.g. an array. In case you'd like to reuse that array, you can also declare it outside the scope of the method:
private static PlantMoveType[] _plantStates =
new []{PlantMoveType.PlantReady, PlantMoveType.PlantRelase};
private bool MyMethod(PlantMoveType plantMoveType)
{
return _plantStates.Contains(plantMoveType);
}
This question already has answers here:
Interesting "params of ref" feature, any workarounds?
(5 answers)
Closed 7 years ago.
I'm not sure if this is easy possible in C#. But I would like to get to know how this could be done easily.
public partial class Form1
{
// I left out the unimportant code for this example
private myControl cLeft,cTop,cBottom,cRight;
private List<myControl>mControls;
public Form1()
{
InitializeComponents();
//this list should contain the fields cLeft,cTop,cBottom,cRight...
mControls=new List<myControl>(){cLeft,cTop,cBottom,cRight};
/* now I want that cLeft and so on get assigned...
of course, this doesn't work because the list refers to the values of
cLeft ... which are null. So I would need to store a reference to those fields to get this work.*/
mControls.ForEach(x=>x=new myControl(this));
}
}
I'm sure it could be done through reflection, but I assume that there should be a way to do this easily in C# or isn't it possible?
It's just a simple loop, there is no need to use LINQ. You just need a for loop.
for (int i = 0 ; i < mControls.Count ; i++) {
mControl[i] = new myControl(this);
}
But, there is no need to write cLeft, cTop etc. You can just refer to them using the indexer: mControls[0], mControl[1] etc.
And remember, the foreach loop or the ForEach extension method doesn't work. This is because you are changing the reference of the variable. That is just another confusing (for beginners) feature of reference types!
Consider this method
public void ChangeReference (string s) {
s = "Hello";
}
And you call this method:
String s = "xxx";
ChangeReference (s);
Will s be "Hello" after the call? No. In the method, you are changing the location of the string in memory, but the argument is still in the same place!