Gregor.

If you've got a DateTime instance, just call myDate.ToString(); you can optionally specify a format-string or predefined culture settings to get the right format (e.g. myDate.ToString("yyyy-MM-dd"); or myDate.ToString(CultureInfo.CurrentCulture); )

In .NET, every class inherits Object's .ToString() method, by default this method simply returns some basic information gained from Reflection, but some types (such as DateTime) override the behaviour. There is also the System.Convert class, but I find myself rarely using it (since it's nothing you can't do with the existing .TryParse / .Parse / .ToString methods.

W3bbo said:

An "int" date?

 

If you've got a DateTime instance, just call myDate.ToString(); you can optionally specify a format-string or predefined culture settings to get the right format (e.g. myDate.ToString("yyyy-MM-dd"); or myDate.ToString(CultureInfo.CurrentCulture); )

 

In .NET, every class inherits Object's .ToString() method, by default this method simply returns some basic information gained from Reflection, but some types (such as DateTime) override the behaviour. There is also the System.Convert class, but I find myself rarely using it (since it's nothing you can't do with the existing .TryParse / .Parse / .ToString methods.

Yeah I wonder if the OP meant:

an International Date ?

or possibly some long int format like 12252009 ?

figuerres said:

W3bbo said:

*snip*

Yeah I wonder if the OP meant:

 

an International Date ?

or possibly some long int format like 12252009 ?

 

If its a date or time value stored in an integer representation of something like ticks or miliseconds then it's trivial, just multiply and cast to long to get ticks, then use DateTime's ticks constructor.

If it's something like 25122009 then the OP has my sympathy, how does something like that happen?

Well, if it is like 25122009 then convert it to a digit array (might as well just convert to a string) then extract the bits you need, then convert to int or datetime:

String input = 25122009.ToString();

String dayStr = input.Substring(0,2);

String monStr = input.Substring(2,2);

String yerStr = input.Substring(4,4);

DateTime date = new DateTime( int.Parse( dayStr ), int.Parse(monStr), int.Parse(yerStr) );

W3bbo said:

An "int" date?

 

If you've got a DateTime instance, just call myDate.ToString(); you can optionally specify a format-string or predefined culture settings to get the right format (e.g. myDate.ToString("yyyy-MM-dd"); or myDate.ToString(CultureInfo.CurrentCulture); )

 

In .NET, every class inherits Object's .ToString() method, by default this method simply returns some basic information gained from Reflection, but some types (such as DateTime) override the behaviour. There is also the System.Convert class, but I find myself rarely using it (since it's nothing you can't do with the existing .TryParse / .Parse / .ToString methods.

I'm no good at this, this is my code.

there is an error on the line, [string mydate..... ]and the next one ????????

int thedate = this.dateTimePicker1.Value.Day & this.dateTimePicker1.Value.Month & this.dateTimePicker1.Value.Year;

string mydate = thedate.ToString;

this.richTextBox1.SaveFile(mydate);

W3bbo said:

An "int" date?

 

If you've got a DateTime instance, just call myDate.ToString(); you can optionally specify a format-string or predefined culture settings to get the right format (e.g. myDate.ToString("yyyy-MM-dd"); or myDate.ToString(CultureInfo.CurrentCulture); )

 

In .NET, every class inherits Object's .ToString() method, by default this method simply returns some basic information gained from Reflection, but some types (such as DateTime) override the behaviour. There is also the System.Convert class, but I find myself rarely using it (since it's nothing you can't do with the existing .TryParse / .Parse / .ToString methods.

I got it you need () at the end of tostring !

C# is new to me. Why does it not do the () in the dot completion system ?

I got another question... In VB I use On Error Resume Next for errors, I need to write files and at times a file does not exist so i use the Error Handling to keep the code running. But I don't know how to do this in C# ???

Thanks for help.

The point being, ToString isn't a property of an object.. it is a method.. a method that says, give me a string representation of this object.

(skipping your above code which I'm sure someone else will comment on).

W3bbo said:

figuerres said:

*snip*

If its a date or time value stored in an integer representation of something like ticks or miliseconds then it's trivial, just multiply and cast to long to get ticks, then use DateTime's ticks constructor.

 

If it's something like 25122009 then the OP has my sympathy, how does something like that happen?

 

Well, if it is like 25122009 then convert it to a digit array (might as well just convert to a string) then extract the bits you need, then convert to int or datetime:

 

String input = 25122009.ToString();

String dayStr = input.Substring(0,2);

String monStr = input.Substring(2,2);

String yerStr = input.Substring(4,4);

 

DateTime date = new DateTime( int.Parse( dayStr ), int.Parse(monStr), int.Parse(yerStr) );

Converting to string, substringing and parsing to integers is not really nice. And the DateTime-constructor you use is used wrongly: the first argument is the year and not the day.

Long live integer division and modulo:

int d = 25122009;
DateTime date =
  new DateTime(
    d / 1000000,
    (d / 10000) % 100,
    d % 10000);

TommyCarlier said:

W3bbo said:

*snip*

Converting to string, substringing and parsing to integers is not really nice. And the DateTime-constructor you use is used wrongly: the first argument is the year and not the day.

Long live integer division and modulo:

int d = 25122009;
DateTime date =
  new DateTime(
    d / 1000000,
    (d / 10000) % 100,
    d % 10000);

Why can the first argument not be the day ?

peoples said:

TommyCarlier said:

*snip*

Why can the first argument not be the day ?

... err because thats the way the constructor is defined? since the parameters aren't named, the order is very important.. how would the callee code know your intent when the intent is in your mind.

http://msdn.microsoft.com/en-us/library/xcfzdy4x.aspx

Also, you stated a few times that c# is confusing vs vb, but these concepts (parenthesis, dot notation and param order) are absolutely fundamentals of many languages, especially the most popular ones... (even vb which you claim to know well)

peoples said:

W3bbo said:

*snip*

I'm no good at this, this is my code.

there is an error on the line, [string mydate..... ]and the next one ????????

 

int thedate = this.dateTimePicker1.Value.Day & this.dateTimePicker1.Value.Month & this.dateTimePicker1.Value.Year;

string mydate = thedate.ToString;

this.richTextBox1.SaveFile(mydate);

Your code won't work. In C# the '&' operator is bitwise AND, so your code is doing the bitwise AND of the integer representations of day, month, and year, which is meaningless.

Just do this:

DateTime myDate = myDateTimePicker.Value;

String dateAsAString = myDate.ToString();

TommyCarlier said:

W3bbo said:

*snip*

Converting to string, substringing and parsing to integers is not really nice. And the DateTime-constructor you use is used wrongly: the first argument is the year and not the day.

Long live integer division and modulo:

int d = 25122009;
DateTime date =
  new DateTime(
    d / 1000000,
    (d / 10000) % 100,
    d % 10000);

Indeed, string conversion is hackish, but it has the benefit of being human-readable without needing to think too much about base-10 division.

As for why I got the parameters wrong: I was getting it right in principle, I wasn't intending for my code to be taken verbatim (and if they did, it's a good exercise in why it's a good idea not to, so I can argue I got it wrong intentionally ).

peoples said:

W3bbo said:

*snip*

I got it you need () at the end of tostring !

 

C# is new to me. Why does it not do the () in the dot completion system ?

 

I got another question... In VB I use On Error Resume Next for errors, I need to write files and at times a file does not exist so i use the Error Handling to keep the code running. But I don't know how to do this in C# ???

 

Thanks for help.

For error handling, you're meant to use Try/Catch and Exceptions; The "On Error Do Something" in VB.NET is meant as a crutch for backwards compatibility with VB6 (i.e. never use it in new projects).

To see if a file exists or not:

try {

    FileStream fs = new FileStream("path to file");

} catch(FileNotFoundException fex) {

}

...of course, you should never use exceptions for normal program flow, it's much better to test first:

try {

    if( File.Exists("path to file") ) {

        // do file operation here

    } else {

        // show error message to user

    }

} catch(IOException ex) {

}

And as you're using C#, you might as well make use of the using() {} block to ensure your program doesn't shít itself if something bad happens in the file IO ops.

W3bbo said:

peoples said:

*snip*

For error handling, you're meant to use Try/Catch and Exceptions; The "On Error Do Something" in VB.NET is meant as a crutch for backwards compatibility with VB6 (i.e. never use it in new projects).

 

To see if a file exists or not:

 

try {

    FileStream fs = new FileStream("path to file");

} catch(FileNotFoundException fex) {

}

 

...of course, you should never use exceptions for normal program flow, it's much better to test first:

 

try {

    if( File.Exists("path to file") ) {

        // do file operation here

    } else {

        // show error message to user

    }

} catch(IOException ex) {

}

 

And as you're using C#, you might as well make use of the using() {} block to ensure your program doesn't shít itself if something bad happens in the file IO ops.

Thanks

peoples said:

W3bbo said:

*snip*

Thanks

What does "master of baiters" mean

As for your code, the Value property of the DateTimePicker is already a DateTime type (similar to VB's Date type). Just call ToString() on the Value property and you'll get the default string representation of the date.

spivonious said:

I think you'd benefit by a good book on C#.

 

As for your code, the Value property of the DateTimePicker is already a DateTime type (similar to VB's Date type). Just call ToString() on the Value property and you'll get the default string representation of the date.

Can you recommend a good book for C# ?

peoples said:

spivonious said:

*snip*

Can you recommend a good book for C# ?

Just one more question, I think if you call the datetime value you get a format like 11/12/2009, is it just a case of parseing out the "/" to make up the file name I want to use it as ?

Thanks

peoples said:

peoples said:

*snip*

Just one more question, I think if you call the datetime value you get a format like 11/12/2009, is it just a case of parseing out the "/" to make up the file name I want to use it as ?

 

Thanks

Its better to do something like

string filename = string.format("d:\\logs\\{0}{1}{2}.log", myDate.Day, myDate.Month, myDate.Year);

Date.ToString() looks different depending on the local of the user, so parsing out / wont work for instance for german versions of windows (+ its really ugly).

the_corona said:

peoples said:

*snip*

Its better to do something like

 

string filename = string.format("d:\\logs\\{0}{1}{2}.log", myDate.Day, myDate.Month, myDate.Year);

 

Date.ToString() looks different depending on the local of the user, so parsing out / wont work for instance for german versions of windows (+ its really ugly).

That's not necessary. If you want to be culture independent, just use the invariant culture:

string filename = string.Format(CultureInfo.InvariantCulture, @"D:\logs\{0:ddMMyyyy}.log", myDate)

This would have the same general effect as your code, without having to do manual date formatting.

Sven Groot said:

the_corona said:

*snip*

That's not necessary. If you want to be culture independent, just use the invariant culture:

 

string filename = string.Format(CultureInfo.InvariantCulture, @"D:\logs\{0:ddMMyyyy}.log", myDate)

 

This would have the same general effect as your code, without having to do manual date formatting.

ah, yes thats interesting, though I've never seen this before. I have to wonder though why you need to specify culturinvariant in that example given you very specifically ask for ddMMyyyy ?

But come to think of it, Date.ToString I think also has an overload to do the formating the way you want, so even something like myDate.ToString("ddMMYYYY") - (I'm not sure of the exact syntax) - could get you a culture invariant string.

Thinking about this more. does the {0:xx} in string.format end up as a string parameter to the first argument's ToString(string format)

overload? So it ends up like

string.format("{0:xx}", myDate) == string.format("{0}", myDate.ToString("xx"));

Does this work in general or only with DateTime?

the_corona said:

Sven Groot said:

*snip*

ah, yes thats interesting, though I've never seen this before. I have to wonder though why you need to specify culturinvariant in that example given you very specifically ask for ddMMyyyy ?

 

But come to think of it, Date.ToString I think also has an overload to do the formating the way you want, so even something like myDate.ToString("ddMMYYYY") - (I'm not sure of the exact syntax) - could get you a culture invariant string.

 

Thinking about this more. does the {0:xx} in string.format end up as a string parameter to the first argument's ToString(string format)

overload? So it ends up like

string.format("{0:xx}", myDate) == string.format("{0}", myDate.ToString("xx"));

Does this work in general or only with DateTime?

 

 

It works because the formatting system has an interface IFormattable which any type can implement, it specifies the type then must have a method ToString(string format, IFormatProvider formatProvider).

The string 'format' would be the part after the colon in String.Format, and of course you can call it directly as in your example of myDate.ToString("ddMMYYYY") (which is actually an overload that doesn't require you to specify the format provider).

The String.Format method works by scanning for the curly brace syntax, if it detects the colon then the following characters until the closing brace are considered the format, if the argument in question is IFormattable then it passes in the format with a format provider it either discovered itself or you provided in the Format call.

If the type isn't formattable it simply calls ToString on it to get a string value.

So if you want your type to have its own custom formatting like:

string.Format("{0:omgbbq}", instanceofmytype).

You simply need to implement IFormattable on your type and do the work to process what the format ('omgbbq' in this case) should mean.

The format providers role is to allow 'outsiders' to specify their own formatter (ICustomFormatter) (albiet imo somewhat convolutedly).

The concept when implementing is.. is a format provider was given, try and get a custom formatter from it, if you get one use that.. otherwise use your own built in formatting.

stevo_ said:

the_corona said:

*snip*

It works because the formatting system has an interface IFormattable which any type can implement, it specifies the type then must have a method ToString(string format, IFormatProvider formatProvider).

 

The string 'format' would be the part after the colon in String.Format, and of course you can call it directly as in your example of myDate.ToString("ddMMYYYY") (which is actually an overload that doesn't require you to specify the format provider).

 

The String.Format method works by scanning for the curly brace syntax, if it detects the colon then the following characters until the closing brace are considered the format, if the argument in question is IFormattable then it passes in the format with a format provider it either discovered itself or you provided in the Format call.

 

If the type isn't formattable it simply calls ToString on it to get a string value.

 

So if you want your type to have its own custom formatting like:

 

string.Format("{0:omgbbq}", instanceofmytype).

 

You simply need to implement IFormattable on your type and do the work to process what the format ('omgbbq' in this case) should mean.

 

The format providers role is to allow 'outsiders' to specify their own formatter (ICustomFormatter) (albiet imo somewhat convolutedly).

 

The concept when implementing is.. is a format provider was given, try and get a custom formatter from it, if you get one use that.. otherwise use your own built in formatting.

Awesome, thnx for the clear explanation. Learned something valuable today!

the_corona said:

Sven Groot said:

*snip*

ah, yes thats interesting, though I've never seen this before. I have to wonder though why you need to specify culturinvariant in that example given you very specifically ask for ddMMyyyy ?

 

But come to think of it, Date.ToString I think also has an overload to do the formating the way you want, so even something like myDate.ToString("ddMMYYYY") - (I'm not sure of the exact syntax) - could get you a culture invariant string.

 

Thinking about this more. does the {0:xx} in string.format end up as a string parameter to the first argument's ToString(string format)

overload? So it ends up like

string.format("{0:xx}", myDate) == string.format("{0}", myDate.ToString("xx"));

Does this work in general or only with DateTime?

 

 

You need to specify InvariantCulture because even with a simple format like that it might have unexpected results if you use the current culture. For instance, the culture might not even use the western calendar!

For example, if I do this:

CultureInfo culture = new CultureInfo("ja-JP");
// Japanese culture settings uses Western calendar by default; might not be true for all cultures though.
culture.DateTimeFormat.Calendar = new JapaneseCalendar();
Thread.CurrentThread.CurrentCulture = culture;

string result = myDate.ToString("ddMMyyyy");

In this case, I've changed the current culture to something that uses a different calendar. Now, if myDate is December 29th 2009, the string result will be "291221". Why? Because on the Japanese calendar, the current year is Heisei 21.

It's easily imaginable that on some system, somewhere, the default culture will be set to something that doesn't produce the correct result even with the format string "ddMMyyyy". That's why you always specify the InvariantCulture if you need a specific result, even if you think it doesn't matter.

Sven Groot said:

the_corona said:

*snip*

You need to specify InvariantCulture because even with a simple format like that it might have unexpected results if you use the current culture. For instance, the culture might not even use the western calendar!

 

For example, if I do this:

CultureInfo culture = new CultureInfo("ja-JP");
// Japanese culture settings uses Western calendar by default; might not be true for all cultures though.
culture.DateTimeFormat.Calendar = new JapaneseCalendar();
Thread.CurrentThread.CurrentCulture = culture;

string result = myDate.ToString("ddMMyyyy");

 

In this case, I've changed the current culture to something that uses a different calendar. Now, if myDate is December 29th 2009, the string result will be "291221". Why? Because on the Japanese calendar, the current year is Heisei 21.

 

It's easily imaginable that on some system, somewhere, the default culture will be set to something that doesn't produce the correct result even with the format string "ddMMyyyy". That's why you always specify the InvariantCulture if you need a specific result, even if you think it doesn't matter.

It's a pity that .NET doesn't make a distinction between "data strings" and "display strings". I mean, instead of ToString() you'd have ToDataString() which returns a culture-independent string of data, and ToDisplayString() which returns a culture-dependent string used for display purposes.

In my own code, I've created some static classes with extension methods to convert values (int, long, DateTime, ...) to data strings and back. You can then write code like this:

DateTime d = DateTime.Today;
string s = d.ToDataString(); // s will be "2009-12-29"
d = s.ToDateTime();

It also knows about nullable values, so you can use s.ToDateTimeOrNull() or convert nullable DateTime to data string.

You can find the code on CodePlex (in folder TC/src/TC.Core in the files ConvertXXX.cs).

TommyCarlier said:

Sven Groot said:

*snip*

It's a pity that .NET doesn't make a distinction between "data strings" and "display strings". I mean, instead of ToString() you'd have ToDataString() which returns a culture-independent string of data, and ToDisplayString() which returns a culture-dependent string used for display purposes.

In my own code, I've created some static classes with extension methods to convert values (int, long, DateTime, ...) to data strings and back. You can then write code like this:

DateTime d = DateTime.Today;
string s = d.ToDataString(); // s will be "2009-12-29"
d = s.ToDateTime();

It also knows about nullable values, so you can use s.ToDateTimeOrNull() or convert nullable DateTime to data string.

You can find the code on CodePlex (in folder TC/src/TC.Core in the files ConvertXXX.cs).

Because ToDataString is essentially the same thing as serialisation, and there are dedicated classes for that. I'm happy with the current simplistic design and I don't feel it needs to be refactored any. If a class has a meaningful culture-specific string representation then always use the IFormatProvider overload.

TommyCarlier said:

Sven Groot said:

*snip*

It's a pity that .NET doesn't make a distinction between "data strings" and "display strings". I mean, instead of ToString() you'd have ToDataString() which returns a culture-independent string of data, and ToDisplayString() which returns a culture-dependent string used for display purposes.

In my own code, I've created some static classes with extension methods to convert values (int, long, DateTime, ...) to data strings and back. You can then write code like this:

DateTime d = DateTime.Today;
string s = d.ToDataString(); // s will be "2009-12-29"
d = s.ToDateTime();

It also knows about nullable values, so you can use s.ToDateTimeOrNull() or convert nullable DateTime to data string.

You can find the code on CodePlex (in folder TC/src/TC.Core in the files ConvertXXX.cs).

Tommy it can get even worse than that.....

if you make a web service that passes a datetime to a client (or client to server) if the client and server are in different timezones the date and time will not be right!

the soap dattime is just a date and time string with no timezone info.

and .net make the date a "local" timezone based date.

in some stuff i do i have to pass the datetime as a string to avoid some issues with that.

i also have an app that has to convert date and time across timezones and has to show 2 date-time values for a given event.

one is always eastern US time and the other can be anywhere... when i first set that up i had folks telling me it was wrong cuse they did not understand the nutty rules that some locales have for when to add or subtract time from UTC / zero.

Sven Groot said:

the_corona said:

*snip*

You need to specify InvariantCulture because even with a simple format like that it might have unexpected results if you use the current culture. For instance, the culture might not even use the western calendar!

 

For example, if I do this:

CultureInfo culture = new CultureInfo("ja-JP");
// Japanese culture settings uses Western calendar by default; might not be true for all cultures though.
culture.DateTimeFormat.Calendar = new JapaneseCalendar();
Thread.CurrentThread.CurrentCulture = culture;

string result = myDate.ToString("ddMMyyyy");

 

In this case, I've changed the current culture to something that uses a different calendar. Now, if myDate is December 29th 2009, the string result will be "291221". Why? Because on the Japanese calendar, the current year is Heisei 21.

 

It's easily imaginable that on some system, somewhere, the default culture will be set to something that doesn't produce the correct result even with the format string "ddMMyyyy". That's why you always specify the InvariantCulture if you need a specific result, even if you think it doesn't matter.

Ah, yes. AFAIK the thai system by default uses the buddist year, so 2009 is 2552.

Quite confusing in fact when you're there

Thread.CurrentThread.CurrentCulture = new CultureInfo("th-th");
Console.WriteLine(DateTime.Now);

Result: 29/12/2552 16:37:51