Develop Reference

Can I shorten this code with a loop in C#?

I have this code written in C# but looks kind of "bad" and I would like to shorten it somehow and keep it clean and simple.
All this code works pretty fine but I want to know if there's any other way I can achieve the same thing.
EDIT: I forgot to mention that the firstLine has a bad date format attached with it, so it is like this: "This_is_my_first_line_20220126". So I split the string and then only join it with the corrected date. The problem is that I can never know how long the new string would be and I don't want to handle the code like this and go up to 100 parts.
Here's my code:
string correctDate = "26012022";
string[] lines = File.ReadAllLines("text.txt");
string firstLine = lines.FirstOrDefault();
//note: firstLine looks like this: This_is_my_first_line_20220126
string[] sub = firstLine.Split('_');
string name="";
if(sub.Length==2)
name = sub[0]+"_"+sub[1]+"_"+correctDate;
else if(sub.Length==3)
name = sub[0]+"_"+sub[1]+"_"+sub[2]+"_"correctDate;
...
else if(sub.Length==20)
name = sub[0]+"_"+ ... "_" + sub[19];
Now, my final name value should be "This_is_my_line_26012022" but I want it to depend on the length of the given string. So far I know that the maximum length would go up to 20 but I don't want my code to look like this. Can I shorten it somehow?

you can find the LastIndexOf the underscore and drop the date by using Substring:
string firstLine = "This_is_my_first_line_20220126";
string correctDate = "26012022";
string correctString = firstLine.Substring(0, firstLine.LastIndexOf("_") + 1) + correctDate;

Still a little perplexed with the split aproach, but this a way to join back all elements
string name = string.Join("_", sub.Take(sub.Length - 1).Append(correctDate));
Or use the substring method (and no need of all that split & join)
name = firstLine.Substring(0, firstLine.LastIndexOf("_") +1) + correctDate;

I forgot to mention that firstLine has a bad date format like "This_is_my_Line_20220125"
If you want to correct just the first line:
string correctDate = "26012022";
string[] lines = File.ReadAllLines("text.txt");
lines[0] = lines[0][..^8] + correctDate;
[..^8] uses C# 9's "indices and ranges" feature, that allows for a more compact way of taking a substring. It means "from the start of the string, up to the index 8 back from the end of the string".
If you get a wiggly line and possibly a messages like "... is not available in C# version X" you can use the older syntax, which would be more like lines[0] = lines[0].Remove(lines[0].Length - 8) + correctDate;
If you want to correct all lines:
string correctDate = "26012022";
string[] lines = File.ReadAllLines("text.txt");
for(int x = 0; x < lines.Length; x++)
lines[x] = lines[x][..^8] + correctDate;
If the incorrect date isn't always 8 characters long, you can use LastIndexOf('_') to locate the last _, and snip it to that point

How to replace text within a string based on their indices

I have a string of text coming from a database. I also have a list of links from a database which have a start index and length correstponding to my string. I want to append the links within the text to be links
<a href=...
I.e
var stringText = "Hello look at http://www.google.com and this hello.co.uk";
This would have in the database
Link:http://www.google.com
Index:14
Length:21
Link:hello.co.uk
Index:45
Length:11
I eventually want
var stringText = "Hello look at http://www.google.com and this hello.co.uk";
There may be many links in the string, so I need a way of looping through these links and replacing based on the index and length. I would just loop through and replace based on the link (string.replace) but causes issues if there are the same link twice
var stringText = "www.google.com www.google.com www.google.com";
www.google.com would become a link and the second time would make the link within the link... a link.
I can obviously find the first index, but if I change it at that point, the index's are no longer valid.
Is there an easy way to do this or am I missing something?

You simply need to remove the subject from source using String.Remove, then use String.Insert to insert your replacement string.
As #hogan suggested in comments you need to sort the replacement list and do the replacement in reverse order (from last to first) to make it work.
If you need to perform many replacements in single string I recommend StringBuilder for performance reasons.

I would use regural expressions.
Take a look at this: Regular expression to find URLs within a string
It might help.

Here's solution without Remove or Insert, or regexes. Just addition.
string stringText = "Hello look at http://www.google.com and this hello.co.uk!";
var replacements = new [] {
new { Link = "http://www.google.com", Index = 14, Length = 21 },
new { Link = "hello.co.uk", Index = 45, Length = 11 } };
string result = "";
for (int i = 0; i <= replacements.Length; i++)
{
int previousIndex = i == 0 ? 0 : replacements[i - 1].Index + replacements[i - 1].Length;
int nextIndex = i < replacements.Length ? replacements[i].Index : replacements[i - 1].Index + replacements[i - 1].Length + 1;
result += stringText.Substring(previousIndex, nextIndex - previousIndex);
if (i < replacements.Length)
{
result += String.Format("{1}", replacements[i].Link,
stringText.Substring(replacements[i].Index, replacements[i].Length));
}
}

String Find & Replace Method

I need to locate a specific part of a string value like the one below, I need to alter the "Meeting ID" to a specific number.
This number comes from a dropdownlist of multiple numbers, so I cant simply use find & replace. As the text could change to one of multiple numbers before the user is happy.
The "0783," part of the string never changes, and "Meeting ID" is always followed by a ",".
So i need to get to "0783, INSERT TEXT ," and then insert the new number on the Index Changed event.
Here is an example :-
Business Invitation, start time, M Problem, 518-06-xxx, 9999 999
0783, Meeting ID, xxx ??
What is the best way of locating this string and replacing the test each time?
I hope this makes sense guys?

Okay, so there are several ways of doing this, however this seems to be a string you have control over so I'm going to say here's what you want to do.
var myString = string.Format("Business Invitation, start time, M Problem, 518-06-xxx, 9999 999 0783, {0}, xxx ??", yourMeetingId);
If you don't have control over it then you're going to have to be a bit more clever:
var startingIndex = myString.IndexOf("0783, ");
var endingIndex = myString.IndexOf(",", startingIndex + 6);
var pattern = myString.Substring(startingIndex + 6, endingIndex - (startingIndex + 6));
myString = myString.Replace(pattern, yourMeetingId);

You should store your "current" Meeting ID in a variable, changing it along with your user's actions, and then use that same global variable whenever you need the string.
This way, you don't have to worry about what's inside the string and don't need to mess with array indexes. You will also be safe from magic numbers / strings, which are bound to blow up in your face at some point in the future.

You can try with Regex.Replace method
string pattern = #"\d{3},";
Regex regex = new Regex(pattern);
var inputStr = "518-06-xxx, 9999 999 0783";
var replace = "..."
var outputStr = regex.Replace(inputStr, replace);

use Regex.Split by token "0783," then in the second string in the array return split by token "," the first element in the string array would be where you would insert new text. Then use string.Join to join the first split with "0783," and the join the second with ",".
string temp = "Business Invitation, start time, M Problem, 518-06-xxx, 9999 999 0783, Meeting ID, xxx ??";
string newID = "1234";
string[] firstSplits = Regex.Split(temp, "0783,");
string[] secondSplits = Regex.Split(firstSplits[1], ",");
secondSplits[0] = newID;
string #join = string.Join(",", secondSplits);
firstSplits[1] = #join;
string newString = string.Join("0783,", firstSplits);

C# - Searching strings

I can't seem to find a good solution to this issue. I've got an array of strings that are fed in from a report that I recieve about lost or stolen equipment. I've been using the string.IndexOf function through the rest of the form and it works quite well. This issue is with the field that says if the device was lost or stolen.
Example:
"Lost or Stolen? Lost"
"Lost or Stolen? Stolen"
I need to be able to read this but when I do string.IndexOf(#"Lost") it will always return lost because it's in the question.
Unfortunately I'm not able to change the form itself in any way and due to the nature of how it's submited I can't just write code the knocks the first 15 or so characters off the string because that may be too few in some cases.
I would really like something in C# that would allow me to continue to search a string after the first result is found so that the logic would look like:
string my_string = "Lost or Stolen? Stolen";
searchFor(#"Stolen" in my_string)
{
Found Stolen;
Does it have "or " infront of it? yes;
ignore and keep searching;
Found Stolen again;
return "Equipment stolen";
}

Couple of options here. You could look for the last index of a space and take the rest of the string:
string input = "Lost or Stolen? Stolen";
int lastSpaceIndex = input.LastIndexOf(' ');
string result = input.Substring(lastSpaceIndex + 1);
Console.WriteLine(result);
Or you could split it and take the last word:
string input = "Lost or Stolen? Lost";
string result = input.Split(' ').Last();
Console.WriteLine(result);
Regex is also an option, but overkill given the simpler solutions above. A nice shortcut that fits this scenario is to use the RegexOptions.RightToLeft option to get the first match starting from the right:
string result = Regex.Match(input, #"\w+", RegexOptions.RightToLeft).Value;

If I understand your requirement, you're looking for an instance of Lost or Stolen after a ?:
var q = myString.IndexOf("?");
var lost = q >= 0 && myString.IndexOf("Lost", q) > 0;
var stolen = q >= 0 && myString.IndexOf("Stolen", q) > 0;
// or
var lost = myString.LastIndexOf("Lost") > myString.IndexOf("?");
var stolen = myString.LastIndexOf("Stolen") > myString.IndexOf("?");
// don't forget
var neither = !lost && !stolen;

You can look for the string 'Lost' and if it occurs twice, then you can confirm it is 'Lost'.

Its possible in this case that you could use index of on a substring knowing that it is always going to say lost or stolen first
so you parse out the lost or stolen, then like for you keyword to match the remaining string.
something like:
int questionIndex = inputValue.indexOf("?");
string toMatch = inputValue.Substring(questionIndex);
if(toMatch == "Lost")

If it works for your use case, it might be easier to use .EndsWith().
bool lost = my_string.EndsWith("Lost");

Remove characters after specific character in string, then remove substring?

I feel kind of dumb posting this when this seems kind of simple and there are tons of questions on strings/characters/regex, but I couldn't find quite what I needed (except in another language: Remove All Text After Certain Point).
I've got the following code:
[Test]
public void stringManipulation()
{
String filename = "testpage.aspx";
String currentFullUrl = "http://localhost:2000/somefolder/myrep/test.aspx?q=qvalue";
String fullUrlWithoutQueryString = currentFullUrl.Replace("?.*", "");
String urlWithoutPageName = fullUrlWithoutQueryString.Remove(fullUrlWithoutQueryString.Length - filename.Length);
String expected = "http://localhost:2000/somefolder/myrep/";
String actual = urlWithoutPageName;
Assert.AreEqual(expected, actual);
}
I tried the solution in the question above (hoping the syntax would be the same!) but nope. I want to first remove the queryString which could be any variable length, then remove the page name, which again could be any length.
How can I get the remove the query string from the full URL such that this test passes?

For string manipulation, if you just want to kill everything after the ?, you can do this
string input = "http://www.somesite.com/somepage.aspx?whatever";
int index = input.IndexOf("?");
if (index >= 0)
input = input.Substring(0, index);
Edit: If everything after the last slash, do something like
string input = "http://www.somesite.com/somepage.aspx?whatever";
int index = input.LastIndexOf("/");
if (index >= 0)
input = input.Substring(0, index); // or index + 1 to keep slash
Alternately, since you're working with a URL, you can do something with it like this code
System.Uri uri = new Uri("http://www.somesite.com/what/test.aspx?hello=1");
string fixedUri = uri.AbsoluteUri.Replace(uri.Query, string.Empty);

To remove everything before the first /
input = input.Substring(input.IndexOf("/"));
To remove everything after the first /
input = input.Substring(0, input.IndexOf("/") + 1);
To remove everything before the last /
input = input.Substring(input.LastIndexOf("/"));
To remove everything after the last /
input = input.Substring(0, input.LastIndexOf("/") + 1);
An even more simpler solution for removing characters after a specified char is to use the String.Remove() method as follows:
To remove everything after the first /
input = input.Remove(input.IndexOf("/") + 1);
To remove everything after the last /
input = input.Remove(input.LastIndexOf("/") + 1);

Here's another simple solution. The following code will return everything before the '|' character:
if (path.Contains('|'))
path = path.Split('|')[0];
In fact, you could have as many separators as you want, but assuming you only have one separation character, here is how you would get everything after the '|':
if (path.Contains('|'))
path = path.Split('|')[1];
(All I changed in the second piece of code was the index of the array.)

The Uri class is generally your best bet for manipulating Urls.

To remove everything before a specific char, use below.
string1 = string1.Substring(string1.IndexOf('$') + 1);
What this does is, takes everything before the $ char and removes it. Now if you want to remove the items after a character, just change the +1 to a -1 and you are set!
But for a URL, I would use the built in .NET class to take of that.

Request.QueryString helps you to get the parameters and values included within the URL
example
string http = "http://dave.com/customers.aspx?customername=dave"
string customername = Request.QueryString["customername"].ToString();
so the customername variable should be equal to dave
regards

I second Hightechrider: there is a specialized Url class already built for you.
I must also point out, however, that the PHP's replaceAll uses regular expressions for search pattern, which you can do in .NET as well - look at the RegEx class.

you can use .NET's built in method to remove the QueryString.
i.e., Request.QueryString.Remove["whatever"];
here whatever in the [ ] is name of the querystring which you want to
remove.
Try this...
I hope this will help.

You can use this extension method to remove query parameters (everything after the ?) in a string
public static string RemoveQueryParameters(this string str)
{
int index = str.IndexOf("?");
return index >= 0 ? str.Substring(0, index) : str;
}