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Raghavendra Reddy C wrote: A similar issue was logged by another person here along with the code
And also a link to the solution.
Use the best guess
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hi,
I am trying to write some data to local port to open the cash drawer....
with this simple code
private void button1_Click(object sender, EventArgs e)
{
serialPort1.Open();
serialPort1.PortName = textBox1.Text;
serialPort1.Write("16 20 1 0 1");
serialPort1.Close();
}
However the Port is not recoginized in C# unless it's a COM port...
My printer somehow say it should be a local port with the name USB_BTP-R880NP_1 (as the name of the printer) .. How can i communicate with it without using a COM command from C#...
Second question is
in the reference, it said to send data to the port to open cash drawer by following this format :
ASCII DLE DC4 n m t
HEx 10 14 n m t
Decimal 16 20 n m t
Range n = 1
m =0,1
1<=t <= 6
Is my command above correct?
Thanks
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Surprisingly, the SerialPort class in C# is designed specifically to talk to serial ports... You cannot talk to a USB device through the SerialPort class, no matter what name you give it. It will only work with COM ports.
Most cash drawers are serial though, are you sure that the cash drawer is connected via usb? If thats the case, you will need to get some sort of driver API to communicate with the usb device through a windows driver and hooks, not a very easy task. Sending raw data to a USB port through the WinAPI involves knowing device descriptors and endpoints that are difficult to know unless you have an intimate knowledge of the driver structure.
As far as your second question, thats something only the manufacturer can tell you. Without having more knowledge on our part, like a manual or interface document, we can't tell you if what you typed is right or wrong.
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Hello All
I am trying to implement MVVM and use IDataErrorInfo interface to validate data in the model classes
I base model class implementing IDataErrorInfo interface
public class BaseClass: IDataErrorInfo
{
<Properties and Members of BaseClass>
#region IDataErrorInfo
public string Error
{
get { return String.Empty; }
}
public string this[string PropertyName]
{
get { return this.GetValidationError(PropertyName); }
}
#endregion
}
Now I want drive a class from Base class
public class DrivedClass: BaseClass
{
}
How do I use IDataErrorInfo members in the derived class to carryout validation of the properties in the derived class??
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You can mark them as virtual and override them in the derived class.
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Okay, declaring arrays is fairly simple… Just like declaring any other variable with the exception of the square brackets.
Initializing one-dimensional arrays also seems fairly simple enough… Initializing two-dimensional arrays is a bit more complicated but still semi-sort of simple if you pay attention to what you're doing.
Jagged arrays, like two-dimensional arrays… Can be a little tricky if you're not paying attention.
I get and understand the declaration and initialization of the jagged arrays, and that you can change the value of any element by re-declaring your array variable…
I'll use the example from the book I'm reading:
(never mind some of the missing closing curly brackets, before I add any more code I want to understand and learn this part first)
using System;
class JaggedClass
{
static void Main ()
{
int[][] myJaggedArray = { new int[] {2, 3, 4}, new int[] {5, 6, 7, 8, 9} };
myJaggedArray[0][0] = 11;
myJaggedArray[1][2] = 22;
Okay, you old pros… Here is the drill/exercise I was supposed to work on:
Drill 4-3
Display the contents of the two-dimensional array called “grades”
that was discussed in this section. Make sure you get the following
result:
Grade=Pass Score=55%
Grade=Good Score=65%
Grade=VeryGood Score=75%
Grade=Distinct Score=85%
The book was showing us three different ways to declare and initialize a two-dimensional arrays.
This is the first way it showed us:
string[,] grades = new string[2, 4] { {"Pass"," Good", "VeryGood", "Distinct"}, {"55%", "65%", "75%", "85%"} };
this is the second way:
string[,] grades = new string[,] { {"Pass", "Good", "VeryGood", "Distinct"}, {"55%", "65%", "75%", "85%"} };
third and final way:
string [,] grades = { {"Pass", "Good", "VeryGood", "Distinct"}, {"55%", "65%", "75%", "85%"} };
I know I probably could have achieved the same result with a "for loop, or a for each loop, maybe even the while loop", but… I couldn't quite figure it out, I beat my head against the wall for almost half an hour trying to figure the loop out… So, I went a different route… The long and hard way… 
It took me about 15 min., maybe even 20 min. to even figure that out… My ah-ha moment came when I accidentally printed to the screen the word "Good"… Don't laugh…  I said don't laugh at! 
I wrote it and I achieved the way it looks in the book, you'll have to compile it in debug it yourself to see what it looks like… I haven't figured out how to format things here in the forum yet.
using System;
using System.Text;
namespace Two_Dimensional_Array
{
class Program
{
static void Main(string[] args)
{
string[,] grades = { { "Pass", "Good", "VeryGood", "Distinct" }, { "55%", "65%", "75%", "85%" } };
string[] gradeScore = {"Grade=", "Score="};
Console.WriteLine(gradeScore[0] + grades[0, 0] + " " + gradeScore[1] + grades[1, 0]);
Console.WriteLine(gradeScore[0] + grades[0, 1] + " " + gradeScore[1] + grades[1, 1]);
Console.WriteLine(gradeScore[0] + grades[0, 2] + " " + gradeScore[1] + grades[1, 2]);
Console.WriteLine(gradeScore[0] + grades[0, 3] + " " + gradeScore[1] + grades[1, 3]);
Console.Read();
}
}
}
modified 22-May-13 21:06pm.
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WidmarkRob wrote: myJaggedArray[0][0] = 11; myJaggedArray[1][2] = 22;
Not quite. A jagged array is essentially an array of arrays. In your sample code, the myJaggedArray variable is an array containing two elements: an array of three integers, and an array of five integers.
myJaggedArray[0] returns the first element, so myJaggedArray[0][0] = 11 is updating the first element of the array stored in the first element of myJaggedArray, and myJaggedArray[1][2] = 22 is updating the third element of the array stored in the second element of myJaggedArray.
http://msdn.microsoft.com/en-us/library/2s05feca.aspx[^]
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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WidmarkRob wrote: the first set of brackets closest to the variable is telling me to access the first element in the jagged array? Then the set of brackets furthest away from the variable is telling me to access the first element, inside of the first element of the jagged array?
Yes, that's correct.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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In addition to Richard Deeming's comments, a 2 dimensional array is just like a square (or oblong) containing N rows, and M columns. So element[0][0] is row 0, column 0, and element[1][2] is row 1 column 2. Try the following for a better illustration:
int[][] myJaggedArray = { new int[] { 2, 3, 4 }, new int[] { 5, 6, 7, 8, 9 } };
for (int N = 0; N < myJaggedArray.GetLength(0); ++N)
{
for (int M = 0; M < myJaggedArray[N].GetLength(0); ++M)
{
Console.WriteLine("element[{0}, {1}] = {2}", N, M, myJaggedArray[N][M]);
}
}
Use the best guess
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one thing I'm going to have to remember about two-dimensional arrays is that the first set of brackets closest to the variable are rows and the second set of brackets are the columns?
Then having to remember if it's a jagged array, the two sets of brackets are accessing the elements differently.
Newbie question… You can declare and initialize brand-new data types and variables in the conditional expression/statement?
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WidmarkRob wrote: and the second set of brackets are the columns?
Exactly, it gets a bit more complicated when you go to 3 or more dimensions.
WidmarkRob wrote: You can declare and initialize brand-new data types and variables in the conditional expression/statement?
Sorry, but I don't understand what you mean by that.
Use the best guess
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This I can see is the start of the for loop with the conditional expression/statement in the parentheses.
You don't have to declare and initialize a variable before starting the for loop?
It looks like you're declaring and initializing a variable as part of the conditional expression/statement and then using the variable right after that…
is my verbiage all wrong?
for (int N = 0; N < myJaggedArray.GetLength(0); ++N)
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Yes, you can declare and initialize the loop control variable in the for statement itself.
http://msdn.microsoft.com/en-us/library/ch45axte.aspx[^]
Note that the scope of that variable is only the loop.
Specifically, you cannot examine that variable after the exiting the loop.
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WidmarkRob wrote: is my verbiage all wrong?
Not really, perhaps, my understanding was. Your question (I think) is about where to declare the loop variable. It is largely a question of where the variable is to be used. Consider the following code:
int index;
for (index = 0; index < someValue; ++index)
{
}
if (index == someOtherValue)
for (int index = 0; index < someValue; ++index)
{
}
if (index == someOtherValue)
Use the best guess
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Richard MacCutchan wrote: myJaggedArray.GetLength(0);
either my book doesn't cover this method you're using or it did and I forgot and I have to go back and read it, I know your buddies book probably covers that, I will read it later…
One other thing, you start talking about two-dimensional arrays and then you post in your code a jagged array.
Jagged Array
int [][]
Two-dimensional Array
int [,]
Right?
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WidmarkRob wrote: Right?
Excactly so; I was merely trying to illustrate how to look at the 'shape' of an array that has only two dimensions. Thinking about it in terms of rows and columns has always helped me when working with arrays.
Use the best guess
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I don't know if you had seen what my drill/exercise was supposed to be… I'm willing to bet a case of beer you be able to figure it out by looking at what I wrote…
I wrote it out the long and hard way… Only because at first, I couldn't quite figure out how to incorporate the for loop.
using System;
using System.Text;
namespace Two_Dimensional_Array
{
class Program
{
static void Main(string[] args)
{
string[,] grades = { { "Pass", "Good", "VeryGood", "Distinct" }, { "55%", "65%", "75%", "85%" } };
string[] gradeScore = {"Grade=", "Score="};
Console.WriteLine(gradeScore[0] + grades[0, 0] + " " + gradeScore[1] + grades[1, 0]);
Console.WriteLine(gradeScore[0] + grades[0, 1] + " " + gradeScore[1] + grades[1, 1]);
Console.WriteLine(gradeScore[0] + grades[0, 2] + " " + gradeScore[1] + grades[1, 2]);
Console.WriteLine(gradeScore[0] + grades[0, 3] + " " + gradeScore[1] + grades[1, 3]);
Console.Read();
}
}
}
After fiddling around with it for a couple of days, I was able to get the for loop in… But, as you'll notice from the code above… The first two lines that print to the screen are spaced out just a little bit further so the Score column is all lined up just like the way they wanted in the book.
Is there some sort of extra C# technique/trick to have the columns line up?
using System;
namespace Two_Dimensional_Array
{
class Program
{
static void Main(string[] args)
{
string[,] grades = { { "Pass", "Good", "VeryGood", "Distinct" }, { "55%", "65%", "75%", "85%" } };
string[] gradeScore = {"Grade=", "Score="};
for (int a = 0; a < 4; a++)
{
Console.WriteLine(gradeScore[0] + grades[0, a] + " " + gradeScore[1] + grades[1, a]);
}
Console.Read();
}
}
}
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WidmarkRob wrote: Is there some sort of extra C# technique/trick to have the columns line up?
Yes, it's all provided by the use of format strings[^], which allow you to specify the width of a field and the alignment of its content. There are also standard shorthand format notations for date, time, currency etc, or you can create your own. So you could code something like:
Console.WriteLine("{0}{1,-8} : {2}{3}", gradeScore[0], grades[0, a], gradeScore[1], grades[1, a]);
Console.WriteLine("Grade={0,-8} : Score={1}", grades[0, a], grades[1, a]);
Use the best guess
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This is one thing C++ programmers must learn really well or you start to run into trouble. C# has taken the dangerous stuff away, but it's now so simple that programmers don't understand what's going on, and when the details matter, it's often tricky because those details are hidden from you.
So, I don't know if this will be helpful or not, but looking at arrays at the low level always helped me...
int x[5];
That's a single-dimensional array - in C++ it's just 5 memory locations (0000-0004) containing int VALUES.
int x[5][5];
That's a two-dimensional array, but it's still LINEAR in memory - it's 25 integers in a row (0000-0024) (note: I'm using decimal memory addresses here for simplicity)
int x[5][];
This is where it gets tricky - that initializes 5 pointers, which point to integer arrays which aren't initialized yet. We have to initialize them, so if we did this...
x[0] = new int[5];
x[1] = new int[2];
....etc...
Now, in x[0] we have a pointer, pointing to a (probably distant) memory location of 5 integers, same as the array in the first example (and x[1] points to a 2-element array). Our x array contains pointers to those other arrays. THAT is a jagged array (x is, not the arrays x points to). See the difference now between the two-dimensional and jagged? A two-dimensional array is just a continuous block of memory with a clever way of indexing it, and that block holds the actual values. A jagged array holds no values, only pointers to other arrays.
And, C++ allows us to do this...
int x[5][5];
x[22] = 42;
....which sets the value "42" in the 23rd element of the array, which is the same as element [4][2] (the third "column" of the 5th "row")
Confused yet?
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I'm not trying to learn C++
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Never the less, you are using a computer, and what I just said there is how a computer works. Understanding what I said there will help you understand C#, which takes what I said and wraps a complicated memory manager around all that. But at the low levels, C# is creating pointers and memory blocks and sticking values in there, and when you say "int x[5];" that is exactly what is happening in C#.
Look at my first paragraph - C# is insulating you from the details which could help you understand arrays.
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if it'll make you feel any better, here is what I'm supposed to bring to the screen:
Grade=Pass Score=55%
Grade=Good Score=65%
Grade=VeryGood Score=75%
Grade=Distinct Score=85%
Drill 4-3
Display the contents of the two-dimensional array called “grades”
that was discussed in this section. Make sure you get the following
result:
I'm not taking any formal classes, but… This is a Drill/Exercise from an e-book I'm reading on C#
I will post my code and ask you fine people for input/feedback about how I did it and maybe how I could have done better…
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Oh, cool 
Please post the link to the e-book you are using, so we can see the context a little better.
My example wasn't about teaching C++, it was about understanding what the computer does when you put certain instructions in C# and the low-level differences between the types of arrays. C# hides those details from you, so you can be more productive, but it reduces understanding. Understanding those low-level concepts can prevent you from creating performance and memory problems in your programs.
Ever wonder why Windows takes twice as much memory to do half as much stuff as Linux? This is why.
EDIT: This is one of the best questions we've got in a long time. I get tired of the "plz snd codez" questions.
modified 20-May-13 17:26pm.
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