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Try statement doesn't always run? [duplicate]

This question already has answers here:
Use of unassigned local variable with try-catch-finally
(4 answers)
Closed last year.
i encountered an error "Use of unassigned variable 'attempt'" when i run the code below, i don't understand the reason because as i understand the try statement block always runs so the variable should be assigned by the user ? Or am i wrong ? If anyone has i fix or work around that would be helpful.
static void MagicNumber(int rndMin, int rndMax, int lives = 4)
{
Random rnd = new Random();
int rndNum = rnd.Next(rndMin, rndMax);
int attempt;
do
{
try
{
Console.WriteLine($"Remaining lives : {lives}");
Console.WriteLine($"Enter a number between {rndMin} and {rndMax} :");
attempt = int.Parse(Console.ReadLine());
}
catch
{
Console.WriteLine("Error : Enter a number !");
}
} while ((lives > 0) || (attempt < rndMin) || (attempt > rndMax));
}
MagicNumber(1, 40, 5);

The variable attempt will not get assigned a value if an exception gets thrown in your try block, so will be unassigned when it gets to the evaluation in your while. The two possible solutions are:
Initialize it to a default value when you declare it.
Assign it some value in your catch block.
Either one should work.

An exception can be thrown in the try block prior to setting a value for attempt. You handle the exception so it's then possible for attempt to be referenced before being assigned a value.
Best practice is to always assign an initial value to variables.

reading data from xml and storing it in variable ,when i am printing variable in console getting error like variable is unassigned in C# [duplicate]

This question already has answers here:
Why did I get the compile error "Use of unassigned local variable"?
(10 answers)
Use of unassigned local variable - if statements
(6 answers)
C# use of unassigned local variable inside an if loop
(2 answers)
Closed 1 year ago.
Here I am attaching code which I am using
{
//reading data from file
XmlTextReader reader = new XmlTextReader(FileLocation);
string s1;
while (reader.Read())
{
//checking whether node name is Esig ang storing Esig value
if (xtr.NodeType==XmlNodeType.Element&&xtr.Name=="Esig")
{
s1=xtr.ReadElementString();
}
}
Console.WriteLine(s1);
}

Local variables aren't initialized. You have to manually initialize them.
Members are initialized, for example:
public class X
{
private string _userName; // This WILL initialize to zero
...
}
But local variables are not:
public static void SomeMethod()
{
string userName; // This is not initialized and must be assigned before used.
...
}
Hence you need to initialize local variable first and then use it.
Your Code will be like
string s1 = string.Empty;
More details are here on Microsoft LINK

C# Conditionally Declare Variables [duplicate]

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.

How to evaluate a string containing local variable names as code in C# [duplicate]

This question already has answers here:
eval(string) to C# code
(8 answers)
Closed 2 years ago.
I need a function to evaluate the value of a string as C# code. The string contains local variables and arithmetic operations, and the function works as if the string is the code in the same place. Something like:
int a = ...; int b = ...; int c = ...;
...
int result = Eval("a+b+c"); // should return current value a+b+c
We can limit the discussion to the simple types like int and arithmetic operations between them. Is it possible to do that in C#/.Net? It is acceptable to pass in context parameter to the function, say, containing the name and value of all required variables.
Thanks!

Prepend script that declares and initializes the variables. For example, if you wish to pass a variable named a into the script, do this:
var script = string.Format("var a = {0}\r\n", a) + script;
var result = Eval(script);

Unassigned Local Variable Error [duplicate]

This question already has answers here:
C# error: Use of unassigned local variable
(4 answers)
Closed 6 years ago.
So I have a folder with only 2 text files, I am reading them and storing the value. This is what the code looks:
public static void UnionFiles()
{
var dinfo =
new DirectoryInfo(
#"\http");
var files = dinfo.GetFiles("*.txt");
int i = 1;
System.Collections.Generic.IEnumerable<String> _eValA, _eValB;
foreach (var file in files)
{
if (i == 1)
{
_eValA = File.ReadLines(file.Name);
++i;
}
else
{
_eValB = File.ReadLines(file.Name);
i = 1;
}
}
IEnumerable<String> union = _eValA.Union(_eValB);
File.WriteAllLines(#"\http\union.txt", union.Cast<String>());
}
But I get this error: Use of unassigned local variable '_eValB, _eValA'
How can I get past it.
Thanks.

The first time through your loop, you will never have both _evalA and _evalB assigned. You need to assign to both to avoid that problem.
There are other related issues. For example, what happens when there aren't exactly two files?
Since there are exactly two files, you shouldn't need to use a loop. If you avoid the loop, you can easily avoid your current issue. For example:
var files = dinfo.GetFiles("*.txt");
System.Collections.Generic.IEnumerable<String> _eValA, _eValB;
// Should really assert that files.Count == 2
_evalA = File.ReadLines(files.First().Name);
_eValB = File.ReadLines(files.Last().Name);
IEnumerable<String> union = _eValA.Union(_eValB);

Think about the possible paths that your code could take. It's possible that _eValA may not be initialized, or that _eValB may not be initialized, and thus you would get an error. Since the compiler can detect this, it gives you a compilation error. You need to make sure they get set equal to a value (or null, which lets the compiler know you're taking responsibility for them, as explained here, but note null wouldn't be appropriate in this case because with 0 or 1 files you'd get an ArgumentNullException at the .Union call) before utilizing them. Try:
var _eValA = new string[0];
var _eValB = new string[0];
foreach (var file in files)
{
if (i == 1)
{
_eValA = File.ReadLines(file.Name);
++i;
}
else
{
_eValB = File.ReadLines(file.Name);
i = 1;
}
}
This will ensure they both get initialized before getting used.