C# Discussion Boards - CodeProject

Re: c# string.IsNullOrEmpty

Bernhard Hiller31-May-16 23:55

Bernhard Hiller

31-May-16 23:55

Eddy Vluggen wrote:
A "null" value in a database is not the same an empty string

You haven't ever worked with an Oracle DB, have you? Big Grin | :-D

Re: c# string.IsNullOrEmpty

Eddy Vluggen1-Jun-16 0:04

Eddy Vluggen

1-Jun-16 0:04

Aw, I did, but it has been a while since Oracle 7 and selecting from 'dual' Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: c# string.IsNullOrEmpty

V.1-Jun-16 1:19

1-Jun-16 1:19

I believe this works in Oracle too?
Confused | :confused:

If issues, please explain, you made me curious... $Shucks | :-\$

(MQOTD rules and previous solutions)

Re: c# string.IsNullOrEmpty

Bernhard Hiller1-Jun-16 4:07

Bernhard Hiller

1-Jun-16 4:07

Well, look at it from a different perspective. Imagine a questionnaire. Someone left a free-text field empty. Does that translate to a null value or string.Empty? Hence an empty string and a null string are the same in an Oracle database. If there's a "not null" constraint on the text field, you cannot insert an empty string either.
At first, I thought that's a WTF. But now I think they got it right.

Re: c# string.IsNullOrEmpty

V.31-May-16 20:09

31-May-16 20:09

As Eddy Vluggen mentioned:

if(dataMySqlReader["user"] != DBNull.Value){
//do this
}
else{
//do that
}

hope this helps.

(MQOTD rules and previous solutions)

modified 1-Jun-16 7:32am.

Re: c# string.IsNullOrEmpty

Richard Deeming1-Jun-16 1:30

Richard Deeming

1-Jun-16 1:30

Won't that produce an InvalidCastException if the field is null?

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Re: c# string.IsNullOrEmpty

V.1-Jun-16 1:32

1-Jun-16 1:32

Oops, my copy/paste error ... D'Oh! | :doh:

I'll fix that...

(MQOTD rules and previous solutions)

Re: c# string.IsNullOrEmpty

aspkiddy1-Jun-16 2:50

aspkiddy

1-Jun-16 2:50

Thanks but it does not work

Re: c# string.IsNullOrEmpty

Eddy Vluggen1-Jun-16 2:52

Eddy Vluggen

1-Jun-16 2:52

What does "not work" mean exactly?

Did it throw an error? If yes, what was the message?

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: c# string.IsNullOrEmpty

aspkiddy1-Jun-16 3:05

aspkiddy

1-Jun-16 3:05

my variable can not affected

Re: c# string.IsNullOrEmpty

Eddy Vluggen1-Jun-16 5:00

Eddy Vluggen

1-Jun-16 5:00

Show us some updated code, maybe we could talk about it Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: c# string.IsNullOrEmpty

V.1-Jun-16 2:52

1-Jun-16 2:52

What's the error ?

Why doesn't it work?

(MQOTD rules and previous solutions)

Re: c# string.IsNullOrEmpty

aspkiddy1-Jun-16 2:56

aspkiddy

1-Jun-16 2:56

But this version works ! Thumbs Up | :thumbsup:

it is very strange Sniff | :^)

/* ......... Sql request ... */

string termUser = String.Empty;
termUser = "callow";   // newwwwwwwww
string catchTerm = String.Empty;

while (dataMySqlReader.Read())
{
    catchTerm = (string)dataMySqlReader["user"];  
        if (catchTerm != null)
        {
            termUser = (string)dataMySqlReader["term"];
        }

}

Re: c# string.IsNullOrEmpty

V.1-Jun-16 3:00

1-Jun-16 3:00

if dataMySqlReader["user"] is null this thing will crash I think...
Note that I updated my previous answer by removing the string cast (that was a copy/paste error)...

also this:

string termUser = String.Empty;
termUser = "callow";   // newwwwwwwww

is useless, use:

string termUser = "callow";

(MQOTD rules and previous solutions)

Re: c# string.IsNullOrEmpty

aspkiddy1-Jun-16 3:08

aspkiddy

1-Jun-16 3:08

but
My variable [termUser] is affected by "callow" with this code : Thumbs Up | :thumbsup:

it is very strange Sniff | :^)

/* ......... Sql request ... */

string termUser = String.Empty;
termUser = "callow";   // newwwwwwwww
string catchTerm = String.Empty;

while (dataMySqlReader.Read())
{
    catchTerm = (string)dataMySqlReader["user"];  
        if (catchTerm != null)
        {
            termUser = (string)dataMySqlReader["term"];
        }

}

Re: c# string.IsNullOrEmpty

Matt T Heffron1-Jun-16 9:25

Matt T Heffron

1-Jun-16 9:25

Just an observation:
Unless the SQL query returns exactly one record, the while loop will end up setting catchTerm to the "user" column from the last record returned, and termUser will be the "term" column from the last record where "user" isn't null (or empty).
Is there a reason that the "user" column can't be checked as part of the SQL query?

"Fairy tales do not tell children the dragons exist. Children already know that dragons exist. Fairy tales tell children the dragons can be killed."
- G.K. Chesterton

Re: c# string.IsNullOrEmpty

aspkiddy2-Jun-16 5:12

aspkiddy

2-Jun-16 5:12

I think if the record does not exist, C # does not fit into the while loop

Re: c# string.IsNullOrEmpty

Matt T Heffron2-Jun-16 6:20

Matt T Heffron

2-Jun-16 6:20

Yes, but if the SQL query returns more than one record, then the effects I mentioned will happen.
If the SQL query is structured to return only a single record (or none), then there's no issue.

"Fairy tales do not tell children the dragons exist. Children already know that dragons exist. Fairy tales tell children the dragons can be killed."
- G.K. Chesterton

Do I Need The Observer Design Pattern In My Situation

MadDashCoder31-May-16 6:12

MadDashCoder

31-May-16 6:12

Suppose I have a hotel app where users can check to see if there is any vacant rooms in my hotel.

The vacancy status changes as old customers checkout and new ones checkin.

Does this situation require the Observer Design Pattern? Also if this is a WCF REST app, how do I simulate multiple people using this app?

modified 31-May-16 12:19pm.

Re: Do I Need The Observer Design Pattern In My Situation

Eddy Vluggen31-May-16 19:42

Eddy Vluggen

31-May-16 19:42

It's not required; you could simply register checkins in a database.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: Do I Need The Observer Design Pattern In My Situation

MadDashCoder1-Jun-16 0:51

MadDashCoder

1-Jun-16 0:51

Hi Eddy, thank you so much for sharing your thought on this.

What is the best way to stress test a WCF RESTful service to simulate multiple users accessing my app?

Re: Do I Need The Observer Design Pattern In My Situation

Eddy Vluggen1-Jun-16 0:57

Eddy Vluggen

1-Jun-16 0:57

I dunno about the "best" way, but you could launch a lot of console-applications making requests Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Back and Forward button for MDI Parent

Rashad Hameed31-May-16 1:26

Rashad Hameed

31-May-16 1:26

VB.NET

Private Sub BACKToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BACKToolStripMenuItem.Click
        Try
            Dim t As New Form
            For Each f As Form In Application.OpenForms
                If f IsNot Me.ActiveMdiChild Then
                    t = f
                Else
                    t.Activate()
                    Return
                End If
            Next
        Catch ex As Exception
            System.Windows.Forms.MessageBox.Show(ex.Message, "Error...!!!", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

    Private Sub FORWARDToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FORWARDToolStripMenuItem.Click
        Try
            Dim t As New Form
            For i As Integer = Application.OpenForms.Count - 1 To 0 Step -1
                Dim f As Form = Application.OpenForms(i)
                If f IsNot Me.ActiveMdiChild Then
                    t = f
                Else
                    t.Activate()
                    Return
                End If
            Next
        Catch ex As Exception
            System.Windows.Forms.MessageBox.Show(ex.Message, "Error...!!!", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

i converted this code to c#

private void BACKToolStripMenuItem_Click(System.Object sender, System.EventArgs e)
{
	try {
		Form t = new Form();
		foreach (Form f in Application.OpenForms) {
			if (!object.ReferenceEquals(f, this.ActiveMdiChild)) {
				t = f;
			} else {
				t.Activate();
				return;
			}
		}
	} catch (Exception ex) {
		System.Windows.Forms.MessageBox.Show(ex.Message, "Error...!!!", MessageBoxButtons.OK, MessageBoxIcon.Error);
	}
}

private void FORWARDToolStripMenuItem_Click(System.Object sender, System.EventArgs e)
{
	try {
		Form t = new Form();
		for (int i = Application.OpenForms.Count - 1; i >= 0; i += -1) {
			Form f = Application.OpenForms(i);
			if (!object.ReferenceEquals(f, this.ActiveMdiChild)) {
				t = f;
			} else {
				t.Activate();
				return;
			}
		}
	} catch (Exception ex) {
		System.Windows.Forms.MessageBox.Show(ex.Message, "Error...!!!", MessageBoxButtons.OK, MessageBoxIcon.Error);
	}
}

can anyone tell me whats is the error in
Form f = Application.OpenForms(i);

backward is working forward is not working help me plz

Re: Back and Forward button for MDI Parent

OriginalGriff31-May-16 3:00

OriginalGriff

31-May-16 3:00

VB uses round brackets '(' and ')' for both Method calls, and array accesses: C# doesn't.
round brackets indicate a method call:

Form f = Application.OpenForms(i);

while square brackets '[' and ']' indicate an array:

Form f = Application.OpenForms[i];

Since Application.OpenForms is a Collection from the line above:

for (int i = Application.OpenForms.Count - 1; i >= 0; i += -1) {

You need to use square brackets, not round.
But...I'd do it with a foreach:

foreach (Form f in Application.OpenForms)
   {
   if (f != ActiveMdiChild)
      {
      ...

Please, don't grab random chunks of VB and throw them through a code converter - they don't always get it right, and when they don't you need to think about them!

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

Re: Back and Forward button for MDI Parent

Rashad Hameed31-May-16 11:14

Rashad Hameed

31-May-16 11:14

thanks thanks alot

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