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No errors in Visual Studio, Code Executes but something not right C# (updated! problem in String.Insert)

I'm writing a program for schoolwork, that's supposed to generate a 10 000 "movie" list. A single "movie" consist of a string in a form "moviename year director". I say "movie" because movie name and director are supposed to be randomly generated with letters from a-z.
I wrote the following logic to generate one such "movie". Movie name and director are random letter combination in length between 4-10 charachters. Code gives no errors in visual studio, executes, but shows blank. If I wrote correctly, then this code should generate one such string and print it, yet console is blank.
Do while loop is there to check if, however unlikely, there is a double item in the List (this is for when I do the 10 000 version).
In short, I dont understand what am I doing wrong?
using System;
using System.Collections.Generic;
using System.Linq;
namespace Experiment
{
class Program
{
static void Main(string[] args)
{
Movies();
Console.ReadKey();
}
public static void Movies()
{
List<string> movieList = new List<string>();
bool check = false;
do
{
string movie = "";
for (int i = 0; i < GetNum(); i++)
{
movie.Insert(0, Convert.ToString(GetLetter()));
}
movie.Insert(0, " ");
movie.Insert(0, Convert.ToString(GetYear()));
movie.Insert(0, " ");
for (int i = 0; i < GetNum(); i++)
{
movie.Insert(0, Convert.ToString(GetLetter()));
}
if (movieList.Contains(movie))
{
check = false;
}
else
{
movieList.Add(movie);
check = true;
}
} while (check == false);
Console.WriteLine(movieList[0]);
}
public static Random _random = new Random();
public static char GetLetter()
{
int num = _random.Next(0, 26);
char let = (char)('a' + num);
return let;
}
public static int GetNum()
{
int num = _random.Next(4, 11);
return num;
}
public static int GetYear()
{
int num = _random.Next(1920, 2020);
return num;
}
}
}

Strings are immutable, so calling the Insert() method on the movie string doesn't do anything to the current movie variable. Instead it returns the new string.
You are however better off changing the movie type from string to StringBuilder, which is a dynamically allocated buffer of characters, so your example becomes:
using System;
using System.Text;
using System.Collections.Generic;
namespace sotest
{
class Program
{
static void Main(string[] args)
{
Movies();
Console.ReadKey();
}
public static void Movies()
{
List<string> movieList = new List<string>();
bool check = false;
do
{
StringBuilder movie = new StringBuilder();
for (int i = 0; i < GetNum(); i++)
{
movie.Insert(0, Convert.ToString(GetLetter()));
}
movie.Insert(0, " ");
movie.Insert(0, Convert.ToString(GetYear()));
movie.Insert(0, " ");
for (int i = 0; i < GetNum(); i++)
{
movie.Insert(0, Convert.ToString(GetLetter()));
}
if (movieList.Contains(movie.ToString()))
{
check = false;
}
else
{
movieList.Add(movie.ToString());
check = true;
}
} while (check == false);
Console.WriteLine(movieList[0]);
}
public static Random _random = new Random();
public static char GetLetter()
{
int num = _random.Next(0, 26);
char let = (char)('a' + num);
return let;
}
public static int GetNum()
{
int num = _random.Next(4, 11);
return num;
}
public static int GetYear()
{
int num = _random.Next(1920, 2020);
return num;
}
}
}

The problem is that you are using movie.Insert incorrectly.
If you read the documentation for String.Insert it says
https://learn.microsoft.com/en-us/dotnet/api/system.string.insert?view=netframework-4.8
Returns a new string in which a specified string is inserted at a
specified index position in this instance
public string Insert (int startIndex, string value);
So it returns a new String, it does not amend the existing one. So you would need to do.
movie = movie.Insert(0, Convert.ToString(GetYear()));
However, I must also say that using String.Insert in this way is not the best approach.
You should instead look at using the StringBuilder class. It is very efficient when you want to amend strings (which are immutable objects).
You might want to read parts of this to help you understand. If you scroll down then it also suggests StringBuilder.
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/strings/

Insert() method is used to return a new string from the specified string at a specified index position. In your case, you are not capturing the updated string.
The best approach to solve this is through using StringBuilder object. Please note that StringBuilder object is much efficient rather than playing with immutable string.

How to parse a multi-lined lambda statement string into DynamicExpression.ParseLambda?

I want to pass a multi-statement lambda string (a little program in fact) into DynamicExpression.ParseLambda but I fear I may have reached its limitations. I have written code to feed small lambda expressions but I think it will choke on a full program.
Here is MCVE so far. It shows the original algorithm BuildSieve() and also it shows the beginning of lambda equivalent but it fails on first line with exception Unknown identifier 'long'
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using diag=System.Diagnostics;
using myAlias = System.Linq.Dynamic; //install package 'System.Linq.Dynamic' v.1.0.7 with NuGet
namespace LambdaStatement
{
class Program
{
static void Main(string[] args)
{
BuildSieveLambda();
Console.ReadKey();
}
static void BuildSieveLambda()
{
try
{
var pList = new List<ParameterExpression>();
pList.Add(Expression.Parameter(typeof(int), "x"));
LambdaExpression e = myAlias.DynamicExpression.ParseLambda(pList.ToArray(), null, "long n = 2000000;");
}
catch (Exception ex)
{
string msg = GetExMessage(ex);
diag.Debug.WriteLine("DEBUGME: " + msg);
throw new Exception(msg);
}
}
public static string GetExMessage(Exception ex)
{
string ret = ex.Message;
if (ex.InnerException!=null)
{
ret= ret+ ": " + GetExMessage(ex.InnerException);
}
return ret;
}
static void BuildSieve()
{
//https://gist.github.com/gideondsouza/1978926 Sieve of Eratosthenes C# implementation by code Gideon Israel Dsouza
long n = 2000000;
bool[] e = new bool[n];//by default they're all false
for (int i = 2; i < n; i++)
{
e[i] = true;//set all numbers to true
}
//weed out the non primes by finding mutiples
for (int j = 2; j < n; j++)
{
if (e[j])//is true
{
for (long p = 2; (p * j) < n; p++)
{
e[p * j] = false;
}
}
}
}
You may think this is impossible but I've seen some really complicated lambda expressions in C# code, full method implementations in fact. So if the C# compiler or Visual Studio can do this then is there access to that API to programmers?

You need to add n the same way you added x:
pList.Add(Expression.Parameter(typeof(long), "n"));
LamdaExpression e = myAlias.DynamicExpression.ParseLamda(pList.ToArray(), null, "n = 200000");
Although, I admit, I have no idea what this program does, but this is why you get that error. It is reading long in the string as an identifier, instead of a type.

Permutation Algorithm OutOfMemory Exception

Please help me to how to fix OutOfMemory exception using below code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Permutation
{
class Program
{
static void Main(string[] args)
{
CreatePartsByFreezingEachElementOnce("abcedfghijk");
PrintPossiblePermutations(false);
Console.WriteLine("---------------");
PrintPossiblePermutations(true);
Console.ReadLine();
}
static void PrintPossiblePermutations(bool unique)
{
var allPermutations = new List<string>();
foreach (var item in _listWithFreezedKey)
if (item.Item2.Count() == 2)
{
allPermutations.Add(Swap(String.Join(",", item.Item1), item.Item2[0], item.Item2[1]));
allPermutations.Add(Swap(String.Join(",", item.Item1), item.Item2[1], item.Item2[0]));
}
if (unique)
{
var uniuePermutations = allPermutations.Distinct();
// PrintPermutations(uniuePermutations.ToList());
Console.WriteLine(uniuePermutations.Count());
}
else
{
// PrintPermutations(allPermutations);
Console.WriteLine(allPermutations.Count());
}
}
static void PrintPermutations(List<string> permutations)
{
int i = 1;
foreach (var item in permutations)
{
Console.WriteLine(string.Format("{0} :{1}", i, item));
i++;
}
}
static List<Tuple<List<char>, List<char>>> _listWithFreezedKey = new List<Tuple<List<char>, List<char>>>();
static void CreatePartsByFreezingEachElementOnce(string str, List<char> indexToFreeze = null)
{
List<Tuple<List<char>, List<char>>> _innerlistWithFreezedKey = new List<Tuple<List<char>, List<char>>>();
var arr = str.ToCharArray().ToList();
var copy = arr;
if (indexToFreeze == null)
{
indexToFreeze = new List<char>();
}
for (int i = 0; i < arr.Count(); i++)
{
copy = str.ToCharArray().ToList();
var nth = arr[i];
copy.RemoveAt(i);
indexToFreeze.Add(nth);
_listWithFreezedKey.Add(new Tuple<List<char>, List<char>>(indexToFreeze.ToList(), copy));
_innerlistWithFreezedKey.Add(new Tuple<List<char>, List<char>>(indexToFreeze.ToList(), copy));
indexToFreeze.RemoveAt(indexToFreeze.Count() - 1);
}
foreach (var item in _innerlistWithFreezedKey)
{
List<char> l = item.Item2;
CreatePartsByFreezingEachElementOnce(String.Join("", l), item.Item1);
}
}
static string Swap(string frezedPart, char swapChar1, char swapChar2)
{
return frezedPart + "," + swapChar1 + "," + swapChar2;
}
}
}
If you run this code using 10 chrs, it throws out of memory exception. But for 9 chars , it returns result.
It was my interview question to write a code such that it should not go out of memory if big data passed.
Thanks,

Your problem is that you want to generate all permutations at once, instead of generating them one-by-one. You are looking for an algorithm which produces the next permutation.
See the first page of Knuth's book on generating permutations.

I would like to answer my question by myself because it may help someone as well.
I will use Iterator Design Pattern to remove unused elements from memory and will convert collection into sequence.
Thanks,

Trying to find specific word inside string without contain method. code isn't working the way it should

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication18
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Sisesta suvaline tekst-->");
string tekst1 = Console.ReadLine();
// string tekst2 = ("ja");
char jtaht = ('j');
char ataht = ('a');
int jsidOntekstis = 0;
int asidOnTekstis = 0;
int tekstipikkus = tekst1.Length;
int jasidonTekstis = jsidOntekstis + asidOnTekstis;
int jasidEiOleTekstis=1;
for (int i = 0; i < tekstipikkus; i++)
{
if (tekst1[i] == jtaht)
{
jsidOntekstis++;
}
if (tekst1[i] == ataht)
{
asidOnTekstis++;
}
}
// for (int k = 0; i < tekstipikkus; i++)
{
{
if (jasidonTekstis > jasidEiOleTekstis)
{
Console.Write("Ja on tekstis olemas");
}
else
{
Console.Write("Ja-sid ei ole tekstis");
}
}
}
Console.ReadKey();
}
}
}
So This is my code and it isn't working the way it should. My teacher asked me to search for "ja" in text without contain method so we would think more logically. I completed all other exercises but this one. Thank you!

StackOverflow is actually not a place where people DO something for you.
They help you and tell you HOW to do this. This issue contains only the wrong piece of code and question "what's wrong".
First of all, I need to tell you that the first problem is, obviously, the algorithm.
I can't understand what is your code supposed to do because even you don't understand it.
using System;
using System.Text;
namespace ConsoleApplication18
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Where to search -->");
string text = Console.ReadLine();
string pattern = "ja"; // Probably, it is better to get it from Console as well
for (int i = 0; i < text.Length; i++)
{
for (int j = 0; j < pattern.Length; j++)
{
if (text[i+j] == pattern[j] && j == pattern.Length - 1)
Console.WriteLine(i);
if (text[i+j] != pattern[j]) break;
}
}
}
}
}
Here is the (not a best) code which searches for the pattern in the text without Contains method. It iterates through the text string - and if it meets the first character of pattern string - it goes further comparing characters one by one in a row. If the inner loop iterated till the end then it means that text string contains pattern string and outputs it's position. If in any moment characters are not equal then the inner loop breaks and continues the main loop.
Research it and understand it. Then you can solve the problem.

Why can't I find Sum() of this HashSet. says "Arithmetic operation resulted in an overflow."

I was trying to solve this problem projecteuler,problem125
this is my solution in python(just for understanding the logic)
lim = 10**8
total=0
found= set([])
for start in xrange(1,int(lim**0.5)):
s=start**2
for i in xrange(start+1,int(lim**0.5)):
s += i**2
if s>lim:
break
if str(s) == str(s)[::-1]:
found.add(s)
print sum(found)
the same code I wrote in C# is as follows
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
public static bool isPalindrome(string s)
{
string temp = "";
for (int i=s.Length-1;i>=0;i-=1){temp+=s[i];}
return (temp == s);
}
static void Main(string[] args)
{
int lim = Convert.ToInt32(Math.Pow(10,8));
var found = new HashSet<int>();
for (int start = 1; start < Math.Sqrt(lim); start += 1)
{
int s = start *start;
for (int i = start + 1; start < Math.Sqrt(lim); i += 1)
{
s += i * i;
if (s > lim) { break; }
if (isPalindrome(s.ToString()))
{ found.Add(s); }
}
}
Console.WriteLine(found.Sum());
}
}
}
the code debugs fine until it gives an exception at Console.WriteLine(found.Sum()); (line31). Why can't I find Sum() of the set found

The sum is: 2,906,969,179.
That is 759,485,532 greater than int.MaxValue;
Change int to long in var found = new HashSet<long>(); To handle the value.
You can also use uint however instead of long, however I would recommend using long.