Develop Reference

String.Format is not working as expected C#

I'm trying to format content of my file like this:
0126252019-05-06 14:47:06 1098500020
But everytime I'm getting this results:
01262524. 5. 2019. 14:47:08 1098500020
Obliviously date and time are not formated as I wanted.
Here is my code:
StreamWriter file = new System.IO.StreamWriter("C:\\MyMainFolder\\MyFilesFolder\\" + 15050 + ".flr");
file.WriteLine(12625.ToString("D6") + string.Format("{0:yyyy-MM-dd HH:mm:ss}", DateTime.Now + " " + 1098500020));
file.Close();
I've tried to format DateTime.Now as I wrote
string.Format("{0:yyyy-MM-dd HH:mm:ss}"
But looks like its not working
Thanks guys
Cheers!

You are passing DateTime.Now + " " + 1098500020 to string.Format which isn't going to be parsed by that format string you have specified. To fix that you should move the ).
However, you should create the entire string, including the prefix, with string.Format, or for clearer code use string interpolation, for example:
var someInteger = 12625;
var line = $"{someInteger:D6}{DateTime.Now:yyyy-MM-dd HH:mm:ss} 1098500020";

The problem is that + is applied as string concatenation in the expression below:
string.Format("{0:yyyy-MM-dd HH:mm:ss}", DateTime.Now + " " + 1098500020);
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// C# makes this one string, and passes it for formatting.
Moving the concatenation that you plan to do inside the format string will fix the problem:
string.Format("{0:yyyy-MM-dd HH:mm:ss} 1098500020", DateTime.Now);

How do I use an illegal character?

public void CreateCertificate()
{
File.Create($"
{#"C:\Users\Director\Documents\TestCertApp\TestSub\" + thisYear +
" Certificates- " + certType + "\""}{myFileName}.ppt", 1 ,
FileOptions.None);
}
So I need the backslash between certype and filename to show it belongs within the folder and not next to. It says its an illegal character but how would I get the file in the folder without it?

Based on the code that you wrote the file path that will be generated is (based on my own substitutions for the variables):
String thisYear = "2019";
String certType = "UnderGrad";
String myFileName = "myfile";
String fileToCreate = $"{#"C:\Users\Director\Documents\TestCertApp\TestSub\" + thisYear + " Certificates- " + certType + "\""}{myFileName}.ppt";
Debug.Print(fileToCreate);
Will give you this output:
C:\Users\Director\Documents\TestCertApp\TestSub\2019 Certificates- UnderGrad"myfile.ppt
If you notice there is a " before the filename part of myfile.ppt - This is where the Illegal Character comes from.
If you use this code fragment to generate the path:
String basePath = #"C:\Users\Director\Documents\TestCertApp\TestSub\";
String certificateFolder = $"{thisYear} Certificates- {certType}";
String correctFilePath = Path.Combine(basePath, certificateFolder, $"{myFileName}.ppt");
Debug.Print(correctFilePath);
This will result in the output of:
C:\Users\Director\Documents\TestCertApp\TestSub\2019 Certificates- UnderGrad\myfile.ppt
This version has a \ where the previous code had a " and is no longer illegal, but conforms to the requirement that you wrote the files being in the folder.
Something else to note:
You may want to use Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); to get the path to the MyDocuments folder of the user.

Well, the short answer is that you cannot use an illegal character in a path or file name. Otherwise it wouldn't be illegal. :)
But it seems that the problem here is that you though you were adding a backslash (\) character, when really you were adding a double quote (") character. So if everything else is ok, you can just replace "\"" with "\\" and it should work.
Part of the problem is also that you're doing some strange combination of string interpolation, and it makes the code really hard to read.
Instead you can use just string interpolation to simplify your string (I had to use concatenation below to prevent horizontal scrolling, but you could remove it):
string filePath = $#"C:\Users\Director\Documents\TestCertApp\TestSub\{thisYear} " +
$#"Certificates- {certType}\{myFileName}.ppt";
But even better would be to use the Path.Combine method, along with some variables, to make the intent very clear:
var rootDir = #"C:\Users\Director\Documents\TestCertApp\TestSub"
var fileDir = $"{thisYear} Certificates- {certType}"
var fileName = "{myFileName}.ppt";
var filePath = Path.Combine(rootDir, fileDir, fileName);

Issue with string in c#?

I am creating a string in c#.
string jsVersion = #"function getContent() {
var content = " + "\"" + documentString + "\"" + #"
return content;
}";
The documentString variable contains a huge string which have line breaks also. Now in javascript when i load this string the content variable does not contains a valid string (because of line breaks).
Now how can i create a string which is valid even if there is line breaks ?

You can use HttpUtility.JavaScriptStringEncode

Can you use string.format instead of concatenation in this fashion?
An example:
string jsVersion = string.format("function getContent() {var content = '{0}'return content; }",documentString);

This will replace your line breaks with <br/>:-
stringToDecode.replace(/\n/, '<br />')

If you want to get rid of the line breaks just remove # from the sting.
# acts a verbatim for your string and therefor adds the line breaks you entered with your declaration.
string jsVersion = "function getContent() {
var content = " + "\"" + documentString + "\"" + "
return content;
}";
should do the trick.

Issue with forming a string with double quotes

I want to form a string as <repeat><daily dayFrequency="10" /></repeat>
Wherein the value in "" comes from a textboxe.g in above string 10. I formed the string in C# as
#"<repeat><daily dayFrequency=""+ txt_daily.Text + "" /></repeat>" but i get the output as
<repeat><daily dayFrequency="+ txt_daily.Text+ " /></repeat>. How to form a string which includes the input from a textbox and also double quotes to be included in that string.

To insert the value of one string inside another you could consider string.Format:
string.Format("foo {0} bar", txt_daily.Text)
This is more readable than string concatenation.
However I would strongly advise against building the XML string yourself. With your code if the user enters text containing a < symbol it will result in invalid XML.
Create the XML using an XML library.
Related
How can I build XML in C#?

Escape it with \ Back slash. putting # in front wont do it for you
string str = "<repeat><daily dayFrequency=\"\"+ txt_daily.Text + \"\" /></repeat>";
Console.Write(str);
Output would be:
<repeat><daily dayFrequency=""+ txt_daily.Text + "" /></repeat>

You could do it like this:
var str = String.Format(#"<repeat><daily dayFrequency="{0}" /></repeat>",
txt_daily.Text);
But it would be best to have an object that mapped to this format, and serialize it to xml

string test = #"<repeat><daily dayFrequency=" + "\"" + txt_daily.Text + "\"" + "/></repeat>";

How do I create a file based on the date?

string filename = DateTime.Today.ToString() + ".csv";
if(!File.Exists(filename))
File.Create(filename);
I thought this would work but it throws a 'format not supported' error. I just want a csv to be created in the directory alongside my .exe

I think the problem is that converting a DateTime to a string will generate a string with invalid filename characters, such as colons (:) and that will cause the create to fail.
You may want to use a format string to control the generated filename. e.g.
string filename = DateTime.Today.ToString("yyyy-MM-dd") + ".csv";

This is because DateTime.Today.ToString() contains slashes, which are not valid as part of a windows filename.
You can, however, do this: DateTime.Now.ToString("yyyyMMdd")

I'm guessing your locale has / / : (or similar confusing characters) in the date format. You should specify an explicit format - "yyyy MM dd" for example:
string filename = DateTime.Today.ToString("yyyy MM dd",
CultureInfo.InvariantCulture) + ".csv";

As everybody has pointed out, the default DateTime.ToString() formatting has invalid characters in it (for just about any region settings), so that
string filename = DateTime.Now.ToString() + ".csv";
generates a 'filename' like 2/18/2011 4:26:48 PM.csv -- which is invalid
if you want a date-time based name, try
string filename = DateTime.Now.ToString("yyyyMMddhhmmss") + ".csv";
to get something like 2011021804254.csv
you can add more formatting, just as long as it doesn't contain any of the following: \ / : * ? " < > |

Your date has slashes in it, try this instead
string filename = Datetime.Now.Ticks.ToString() + ".csv";