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How do I check if a string contains a string from an array of strings?

So here is my example
string test = "Hello World, I am testing this string.";
string[] myWords = {"testing", "string"};
How do I check if the string test contains any of the following words? If it does contain how do I make it so that it can replace those words with a number of asterisks equal to the length of that?

You can use a regex:
public string AstrixSomeWords(string test)
{
Regex regex = new Regex(#"\b\w+\b");
return regex.Replace(test, AsterixWord);
}
private string AsterixWord(Match match)
{
string word = match.Groups[0].Value;
if (myWords.Contains(word))
return new String('*', word.Length);
else
return word;
}
I have checked the code and it seems to work as expected.
If the number of words in myWords is large you might consider using HashSet for better performance.

bool cont = false;
string test = "Hello World, I am testing this string.";
string[] myWords = { "testing", "string" };
foreach (string a in myWords)
{
if( test.Contains(a))
{
int no = a.Length;
test = test.Replace(a, new string('*', no));
}
}

var containsAny = myWords.Any(x => test.Contains(x));

Something like this
foreach (var word in mywords){
if(test.Contains(word )){
string astr = new string("*", word.Length);
test.Replace(word, astr);
}
}
EDIT: Refined

C# Split string into array based on prior character

I need to take a string and split it into an array based on the type of charcter not matching they proceeding it.
So if you have "asd fds 1.4#3" this would split into array as follows
stringArray[0] = "asd";
stringArray[1] = " ";
stringArray[2] = "fds";
stringArray[3] = " ";
stringArray[4] = "1";
stringArray[5] = ".";
stringArray[6] = "4";
stringArray[7] = "#";
stringArray[8] = "3";
Any recomendations on the best way to acheive this? Of course I could create a loop based on .ToCharArray() but was looking for a better way to achieve this.
Thank you

Using a combination of Regular Expressions and link you can do the following.
using System.Text.RegularExpressions;
using System.Linq;
var str="asd fds 1.4#3";
var regex=new Regex("([A-Za-z]+)|([0-9]+)|([.#]+)|(.+?)");
var result=regex.Matches(str).OfType<Match>().Select(x=>x.Value).ToArray();
Add additional capture groups to capture other differences. The last capture (.+?) is a non greedy everything else. So every item in this capture will be considered different (including the same item twice)
Update - new revision of regex
var regex=new Regex(#"(?:[A-Za-z]+)|(?:[0-9]+)|(?:[#.]+)|(?:(?:(.)\1*)+?)");
This now uses non capturing groups so that \1 can be used in the final capture. This means that the same character will be grouped if its in then catch all group.
e.g. before the string "asd fsd" would create 4 strings (each space would be considered different) now the result is 3 strings as 2 adjacent spaces are combined

Use regex:
var mc = Regex.Matches("asd fds 1.4#3", #"([a-zA-Z]+)|.");
var res = new string[mc.Count];
for (var i = 0; i < mc.Count; i++)
{
res[i] = mc[i].Value;
}

This program produces exactly output you want, but I am not sure wether it's generic enaugh for your goal.
class Program
{
private static void Main(string[] args)
{
var splited = Split("asd fds 1.4#3").ToArray();
}
public static IEnumerable<string> Split(string text)
{
StringBuilder result = new StringBuilder();
foreach (var ch in text)
{
if (char.IsLetter(ch))
{
result.Append(ch);
}
else
{
yield return result.ToString();
result.Clear();
yield return ch.ToString(CultureInfo.InvariantCulture);
}
}
}
}

How can I copy from one string to another string from the desired location to the end?

Suppose I have:
string abc="Your name = Hello World";
using length function I match the existence of an location of the = operator, but how can I copy all the words that come after the =, such as "Hello Word", from this string to another one?

string abc="Your name = Hello World";
abc.Substring(abc.IndexOf("=")+1); //returns " Hello World"

There's several ways to do it. Here are a few examples...
Using Split:
string[] parts = abc.Split(new char[]{'='}, 2);
if (parts.Length != 2) { /* Error */ }
string result = parts[1].TrimStart();
Using IndexOf and Substring:
int i = abc.IndexOf('=');
if (i == -1) { /* Error */ }
string s = abc.Substring(abc, i).TrimStart();
Using a regular expression (probably overkill for this):
Match match = Regex.Match(abc, #"=\s*(.*)");
if (!match.Success) { /* Error */ }
string result = match.Groups[1].Value;

string newstring = abc.Substring(abc.IndexOf("=") + 2);

string abc="Your name = Hello World";
string[] newString = abc.Split('=');
/*
newString[0] is 'Your name '
newString[1] is ' Hello World'
*/

How to remove lowercase on a textbox?

I'm trying to remove the lower case letters on a TextBox..
For example, short alpha code representing the insurance (e.g., 'BCBS' for 'Blue Cross Blue Shield'):
txtDesc.text = "Blue Cross Blue Shield";
string Code = //This must be BCBS..
Is it possible? Please help me. Thanks!

Well you could use a regular expression to remove everything that wasn't capital A-Z:
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main( string[] args )
{
string input = "Blue Cross Blue Shield 12356";
Regex regex = new Regex("[^A-Z]");
string output = regex.Replace(input, "");
Console.WriteLine(output);
}
}
Note that this would also remove any non-ASCII characters. An alternative regex would be:
Regex regex = new Regex(#"[^\p{Lu}]");
... I believe that should cover upper-case letters of all cultures.

string Code = new String(txtDesc.text.Where(c => IsUpper(c)).ToArray());

Here is my variant:
var input = "Blue Cross Blue Shield 12356";
var sb = new StringBuilder();
foreach (var ch in input) {
if (char.IsUpper(ch)) { // only keep uppercase
sb.Append(ch);
}
}
sb.ToString(); // "BCBS"
I normally like to use regular expressions, but I don't know how to select "only uppercase" in them without [A-Z] which will break badly on characters outside the English alphabet (even other Latin characters! :-/)
Happy coding.
But see Mr. Skeet's answer for the regex way ;-)

Without Regex:
string input = "Blue Cross Blue Shield";
string output = new string(input.Where(Char.IsUpper).ToArray());
Response.Write(output);

string Code = Regex.Replace(txtDesc.text, "[a-z]", "");

I´d map the value to your abbreviation in a dictionary like:
Dictionary<string, string> valueMap = new Dictionary<string, string>();
valueMap.Add("Blue Cross Blue Shield", "BCBS");
string Code = "";
if(valueMap.ContainsKey(txtDesc.Text))
Code = valueMap[txtDesc.Text];
else
// Handle
But if you still want the functionality you mention use linq:
string newString = new string(txtDesc.Text.Where(c => char.IsUpper(c).ToArray());

You can try use the 'Replace lowercase characters with star' implementation, but change '*' to '' (blank)
So the code would look something like this:
txtDesc.Text = "Blue Cross Blue Shield";
string TargetString = txt.Desc.Text;
string MainString = TargetString;
for (int i = 0; i < TargetString.Length; i++)
{
if (char.IsLower(TargetString[i]))
{
TargetString = TargetString.Replace( TargetString[ i ].ToString(), string.Empty );
}
}
Console.WriteLine("The string {0} has converted to {1}", MainString, TargetString);

string caps = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string.Join("",
"Blue Cross Blue Shield".Select(c => caps.IndexOf(c) > -1 ? c.ToString() : "")
.ToArray());

Rather than matching on all capitals, I think the specification would require matching the first character from all the words. This would allow for inconsitent input but still be reliable in the long run. For this reason, I suggest using the following code. It uses an aggregate on each Match from the Regex object and appends the value to a string object called output.
string input = "Blue Cross BLUE shield 12356";
Regex regex = new Regex("\\b\\w");
string output = regex.Matches(input).Cast<Match>().Aggregate("", (current, match) => current + match.Value);
Console.WriteLine(output.ToUpper()); // outputs BCBS1

string Code = Regex.Replace(txtDesc.text, "[a-z]", "");

This isn't perfect but should work (and passes your BCBS test):
private static string AlphaCode(String Input)
{
List<String> capLetter = new List<String>();
foreach (Char c in Input)
{
if (char.IsLetter(c))
{
String letter = c.ToString();
if (letter == letter.ToUpper()) { capLetter.Add(letter); }
}
}
return String.Join(String.Empty, capLetter.ToArray());
}
And this version will handle strange input scenarios (this makes sure the first letter of each word is capitalized).
private static string AlphaCode(String Input)
{
String capCase = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(Input.ToString().ToLower());
List<String> capLetter = new List<String>();
foreach (Char c in capCase)
{
if (char.IsLetter(c))
{
String letter = c.ToString();
if (letter == letter.ToUpper()) { capLetter.Add(letter); }
}
}
return String.Join(String.Empty, capLetter.ToArray());
}

formatting string in MVC /C#

I have a string 731478718861993983 and I want to get this 73-1478-7188-6199-3983 using C#. How can I format it like this ?
Thanks.

By using regex:
public static string FormatTest1(string num)
{
string formatPattern = #"(\d{2})(\d{4})(\d{4})(\d{4})(\d{4})";
return Regex.Replace(num, formatPattern, "$1-$2-$3-$4-$5");
}
// test
string test = FormatTest1("731478718861993983");
// test result: 73-1478-7188-6199-3983

If you're dealing with a long number, you can use a NumberFormatInfo to format it:
First, define your NumberFormatInfo (you may want additional parameters, these are the basic 3):
NumberFormatInfo format = new NumberFormatInfo();
format.NumberGroupSeparator = "-";
format.NumberGroupSizes = new[] { 4 };
format.NumberDecimalDigits = 0;
Next, you can use it on your numbers:
long number = 731478718861993983;
string formatted = number.ToString("n", format);
Console.WriteLine(formatted);
After all, .Net has very good globalization support - you're better served using it!

string s = "731478718861993983"
var newString = (string.Format("{0:##-####-####-####-####}", Convert.ToInt64(s));

LINQ-only one-liner:
var str = "731478718861993983";
var result =
new string(
str.ToCharArray().
Reverse(). // So that it will go over string right-to-left
Select((c, i) => new { #char = c, group = i / 4}). // Keep group number
Reverse(). // Restore original order
GroupBy(t => t.group). // Now do the actual grouping
Aggregate("", (s, grouping) => "-" + new string(
grouping.
Select(gr => gr.#char).
ToArray())).
ToArray()).
Trim('-');
This can handle strings of arbitrary lenghs.

Simple (and naive) extension method :
class Program
{
static void Main(string[] args)
{
Console.WriteLine("731478718861993983".InsertChar("-", 4));
}
}
static class Ext
{
public static string InsertChar(this string str, string c, int i)
{
for (int j = str.Length - i; j >= 0; j -= i)
{
str = str.Insert(j, c);
}
return str;
}
}

If you're dealing strictly with a string, you can make a simple Regex.Replace, to capture each group of 4 digits:
string str = "731478718861993983";
str = Regex.Replace(str, "(?!^).{4}", "-$0" ,RegexOptions.RightToLeft);
Console.WriteLine(str);
Note the use of RegexOptions.RightToLeft, to start capturing from the right (so "12345" will be replaced to 1-2345, and not -12345), and the use of (?!^) to avoid adding a dash in the beginning.
You may want to capture only digits - a possible pattern then may be #"\B\d{4}".

string myString = 731478718861993983;
myString.Insert(2,"-");
myString.Insert(7,"-");
myString.Insert(13,"-");
myString.Insert(18,"-");

My first thought is:
String s = "731478718861993983";
s = s.Insert(3,"-");
s = s.Insert(8,"-");
s = s.Insert(13,"-");
s = s.Insert(18,"-");
(don't remember if index is zero-based, in which case you should use my values -1)
but there is probably some easier way to do this...

If the position of "-" is always the same then you can try
string s = "731478718861993983";
s = s.Insert(2, "-");
s = s.Insert(7, "-");
s = s.Insert(12, "-");
s = s.Insert(17, "-");

Here's how I'd do it; it'll only work if you're storing the numbers as something which isn't a string as they're not able to be used with format strings.
string numbers = "731478718861993983";
string formattedNumbers = String.Format("{0:##-####-####-####-####}", long.Parse(numbers));
Edit: amended code, since you said they were held as a string in your your original question