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Strings are not getting concatenated properly [closed]

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i have below code where string dont get concatenated
string postCode = "1245";
string city = "Stockholm";
string postCodeAndCity = postCode ?? " " + " " + city ?? " ";
I get output as 1245. Not sure why it excludes city.
But this line works
string.Concat(postCode??" ", " ", city?? " ");
so why the first approach dont work?

The ?? operator associates like this:
string postCodeAndCity = postCode ?? (" " + " " + city ?? (" "));
So if postCode is not null, it just takes postCode. If postCode is null, then it takes (" " + " " + city ?? (" ")).
You can see this from the precedence table, where ?? has lower precedence than +. Therefore + binds more tightly than ??, i.e. a ?? b + c binds as a ?? (b + c), not as (a ?? b) + c.
However, in:
string.Concat(postCode??" ", " ", city?? " ");
The commas of course have higher precedence than the ??. The equivalent using + would be:
(postCode ?? " ") + " " + (city ?? " ");
I suspect what you might want to do is:
If both postCode and city are not null, take both with a space between them.
If one is null but the other isn't, take the non-null one.
If both are null, take an empty string.
You can write this long-hand:
if (postCode != null)
{
if (city != null)
return postCode + " " + city;
else
return city;
}
else
{
if (postCode != null)
return postCode;
else
return "";
}
You can write this a bit shorter (although slightly more expensively) with:
string.Join(" ", new[] { postCode, city }.Where(x => x != null));

You should use string interpolation for this:
var output = $"{postCode} {city}"
For more information see:
https://learn.microsoft.com/de-de/dotnet/csharp/language-reference/tokens/interpolated

c# transfer list items to listbox [duplicate]

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Binding Listbox to List<object> in WinForms
(8 answers)
Closed 3 years ago.
I write a program, it is necessary to switch the current status in it, as well as it is necessary to plan it when you plan an event, it is perceived as an object, the object has its own fields, such as the start time and end time of the event, I want this object to be output when generated sheet boxing.
Tell me how can this be done?
List<ChangeStatus> events = new List<ChangeStatus>();
private void toPlanButton_Click(object sender, EventArgs e)
{
string comboBoxTypeNumber = comboBoxType.SelectedItem.ToString();
DateTime Time = new DateTime();
Time = dateTimePicker1.Value;
DateTime longTime = new DateTime();
longTime = dateTimePicker2.Value;
ChangeStatus statusEvent = new ChangeStatus();
statusEvent.StartEvent = Time;
statusEvent.LongEvent = longTime;
statusEvent.TypeEvent = comboBoxTypeNumber;
events.Add(statusEvent);
TimeComparer tc = new TimeComparer();
events.Sort(tc);
}
How to display an object in listbox?
It is necessary to display a list of objects, because in the future I want to make editing objects
listBoxEvent.Items.Add("type: " + statusEvent.TypeEvent + ";" + " start: " + statusEvent.StartEvent + ";" + " long: " + statusEvent.LongEvent + " min;"); - work

You can use System.Linq Linq to get the string text and can call the AddRange() method on Items collection like
List<string> listData = events.Select(x => "type: " + x.TypeEvent + ";" + " start: " + x.StartEvent + ";" + " long: " + x.LongEvent + " min;").ToList();
listBoxEvent.DataSource = listData;

How to convert char array into string for DateTime.Parse? [closed]

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I am using this in my controller:
char[] arrDate = date.ToArray();
DateTime dt = DateTime.Parse(arrDate[0] + arrDate[1] + "/" +
arrDate[2] + arrDate[3] + "/" +
arrDate[4] + arrDate[5] + arrDate[6] + arrDate[7]);
The error:
System.FormatException: String was not recognized as a valid DateTime.

Consider this:
var date = "11252017";
var arrDate = date.ToArray();
var strDate = arrDate[0] + arrDate[1] + "/" +
arrDate[2] + arrDate[3] + "/" +
arrDate[4] + arrDate[5] + arrDate[6] + arrDate[7]; // 98/25/2017
Notice that:
'1' + '1' = 98* ⇒ char + char = int
98 + "/" = "98/" ⇒ int + string = string
"98/" + '2' = "98/2" ⇒ string + char = string
The fix:
var dt = DateTime.Parse("" +
arrDate[0] + arrDate[1] + "/" +
arrDate[2] + arrDate[3] + "/" +
arrDate[4] + arrDate[5] + arrDate[6] + arrDate[7]);
*ASCII representation:
'1' in decimal is 49

I assume date is of type string. For parsing a string the DateTime class has several methods of which ParseExact is one. This method can parse a string given a format specifier and a culture. In your case the date can be parsed like this:
var date = "11252017";
var dt = DateTime.ParseExact(date, "MMddyyyy", CultureInfo.InvariantCulture);
By the way a string is an array of chars, so in your code arrDate[0] is exactly the same as date[0]. Just something to keep in mind for the future.

How to link a button to outlook application and send mail c# [closed]

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protected void LinkButton1_Click(object sender, EventArgs e) {
string ContactID = txtContactID.Text;
string EmailMessage = txtEmailContent.Text;
string[] words = ContactID.Split(',');
foreach (string word in words)
{
DataTable dt = reference.SendMultipleEmail_Fetch(Convert.ToInt32(words)).Tables[0];
if (dt.Rows.Count > 0)
{
foreach (DataRow row in dt.Rows)
{
if (row["Email"].ToString() != "" && txtContactID.Text != "" && txtEmailContent.Text != "")
{
Process.Start("mailto:" + row["Email"].ToString() + "?subject=" + "I love you" + "&body=" + "Hi you");
lblInfo.Text = "Message successfully sent";
}
else
{
lblInfo.Text = "Email Content is required or contact not selected";
return;
}
}
}
}
I have a grid table which multiple email addresses can be checked and mailed as a group. am trying to add a link button that will open up outlook and populate with the email addresses checked on the grid and then send mail out

If you just want to open email client window for sending a message, you can use this:
Process.Start("mailto:" + emailAddress + "?subject=" + subject + "&body=" + body);
However, if you just want to send email without any input from the user, best bet would be to send directly via SMTP server. You can use SmtpClient class for that:
https://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient%28v=vs.110%29.aspx

Change "\\server\printer" to "printer on server:" [closed]

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I have a string "\\server\printer" and I need to change it to `"printer on server:"
please note that "server and printer can vary in lengths.

var incomingText = #"\\server\printer";
var split = incomingText.Split(new[] { '\\' }, StringSplitOptions.RemoveEmptyEntries);
var decoratedText = split[1] + " on " + split[0];

String[] split = yourString.Split("\\");
Return split[1] + " on " + split[0];

Here you go
https://dotnetfiddle.net/ZsjrsN
var str = #"\\server\printer";
var matches = Regex.Match(str, #"[A-Za-z0-9]{1,}");
string str1 = matches.Value;
matches = matches.NextMatch();
string str2 = matches.Value;
string result = str2 + " on " + str1;