C# Discussion Boards - CodeProject

Generics: T x = 5 fails [modified]

17-Aug-06 1:44

Hello

Why use a 3rd library. You got all you need in System.Net namespace and namespaces derived from it like System.Net.NetworkInformation

Regards Rose | [Rose]

Tomerland16-Aug-06 22:57

Tomerland

16-Aug-06 22:57

Dear gurus,

I have a generics question.

// T is either Int32 or Double
void fkt<T>( ref T someValue ) where T : IConvertible
{

Int32 i = 5;

someValue = i; <---- compiler error here
someValue = (T)i; <---- compiler error here

}

In both cases I get a type conversion error

How can I handle this? I know in advance, that T is only Int32 or Double.

Thanks for your help

-- modified at 4:58 Thursday 17th August, 2006

Christian Graus16-Aug-06 23:05

16-Aug-06 23:05

T i = 5;

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Tomerland17-Aug-06 0:30

Tomerland

17-Aug-06 0:30

Hallo,

does not work. Still same compiler-error-message

Kind regards

Christian Graus17-Aug-06 0:37

Re: Generics: T x = 5 fails [modified]

17-Aug-06 0:37

void fkt<t>(ref T someValue) where T : IConvertible
{
IConvertible i = 5;

someValue = (T)i;

}

Generics kind of suck. They aren't a pimple on the backside of C++ templates.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Tomerland17-Aug-06 1:27

Tomerland

17-Aug-06 1:27

Wow ! ! !
Thank you ! ! !

You seem to be an absolute expert.

But two new questions arise: -))

1.
From where can I get such know-how? Is there any good book/paper available on such details?

2.
How can I restrict my Generic Type <t> to the basic datatypes as e.g.: char, int, double,..

fct<t>( T value ) where T: ...basic numeric types only ...

Kind regards

-- modified at 7:27 Thursday 17th August, 2006

Christian Graus17-Aug-06 1:40

17-Aug-06 1:40

Tomerland wrote:
From where can I get such know-how? Is there any good book/paper available on such details?

*blush* I googled it. I've only really used generics for typed containers, I was interested enough to know more that I was willing to spend a little time researching it and playing with a sample app.

Tomerland wrote:
How can I restrict my Generic Type to the basic datatypes as e.g.: char, int, double,..

http://msdn2.microsoft.com/en-us/library/d5x73970.aspx[^]

It looks to me like it's not possible.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Nader Elshehabi17-Aug-06 2:07

17-Aug-06 2:07

Hello

Christian Graus wrote:
It looks to me like it's not possible

I believe it is. This method should only work with int and double types only

private void CreateMethod<T>() where T : IComparable<int> , IComparable<double>, new()
        {
            T instance = new T();
            MessageBox.Show(instance.ToString());
        }

Regards

Christian Graus17-Aug-06 2:15

Re: Generics: T x = 5 fails [modified]

17-Aug-06 2:15

This won't compile as you put IComparable twice. However, one fixed, it seems to work with only numeric types. I had no idea you could put

int n = new int();

It seems kind of redundant to me.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Nader Elshehabi17-Aug-06 2:39

17-Aug-06 2:39

Hello

Actually there was an error due to CP script. Sorry I have to remove the pre tag. Here is the correct code

private void CreateMethod<T>() where T : IComparable<int> , IComparable<double>, new()
{
T instance = new T();
MessageBox.Show(instance.ToString());
}

and why you call the new() redundant?? How would you declare your types in the method otherwise??

Regards Rose | [Rose]

-- modified at 8:41 Thursday 17th August, 2006

Christian Graus17-Aug-06 2:47

17-Aug-06 2:47

T instance; ( if T is an int or a double. )

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Enterprise deployment console

eggsovereasy17-Aug-06 4:02

eggsovereasy

17-Aug-06 4:02

Yeah, I didn't know you could use new with value types either. I guess I've just never tried.

abhinish16-Aug-06 22:39

abhinish

16-Aug-06 22:39

hi guys!

need some help..

i have to make a management console type application which will install software on remote machines in a network .. using c#

can any one tell me where to start from..any useful links or tutorial etc..
will using winsock is a good idea?

abhinav

Classes [modified]

Mamphekgo16-Aug-06 22:03

Mamphekgo

16-Aug-06 22:03

Hi.
I have created a class that read data from the database and i want to display this data on labels.

here is my class

public void SeachProduct(string PBarcode,string PName,string PPrice)
{
Barcode = PBarcode;
ProductName = PName;
Price = PPrice;

SqlConnection conn1 = new SqlConnection();
conn1.ConnectionString = "integrated security=SSPI;initial catalog=Phusa;server = za211149;persist security info=False";
conn1.Open();
try
{
SqlCommand cmdSearch1 = new SqlCommand();
cmdSearch1.Connection = conn1;
cmdSearch1.CommandText = "SELECT ProductName,Price FROM Products WHERE Barcode=@Barcode";

SqlParameter Bar = new SqlParameter();
Bar.ParameterName = "@Barcode";
Bar.Direction = System.Data.ParameterDirection.Input;
Bar.Value = Barcode;
cmdSearch1.Parameters.Add(Bar);

SqlParameter Nam1 = new SqlParameter();
Nam1.ParameterName="@ProductName";
Nam1.Direction = System.Data.ParameterDirection.Output;
Nam1.Value =ProductName;
cmdSearch1.Parameters.Add(Nam1);

SqlParameter Pri= new SqlParameter();
Pri.ParameterName = "@Price";
Pri.Direction = System.Data.ParameterDirection.Output;
Pri.Value = Price;
cmdSearch1.Parameters.Add(Pri);

SqlDataReader dr1 =cmdSearch1.ExecuteReader();
if(dr1.Read()==true)
{

//MessageBox.Show("Product found");
ProductName= dr1["ProductName"].ToString();
Price = dr1["Price"].ToString();

}
else
{
MessageBox.Show("Product not found");
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
conn1.Close();
}

and here i am try to call so that it can display data on the labels my class on form

SearchCustomers search = new SearchCustomers();
string Barcode;
string ProductName="";
string Price = "";

Barcode = txtBarcode.Text;

search.SeachProduct(Barcode,ProductName,Price);
lblProductName.Text = ProductName;
lblPrice.Text =Price;
}

-- modified at 4:03 Thursday 17th August, 2006

Re: Classes

Guffa16-Aug-06 22:13

Guffa

16-Aug-06 22:13

To make your code work as it is now, you have to use the "ref" keyword on the parameters, so that the method can change the strings that you send into it:

public void SeachProduct(string PBarcode, ref string PName, ref string PPrice)

and

search.SeachProduct(Barcode, ref ProductName, ref Price);

To use reference parameters in this ways is rarely used, though. Store the values in the search object instead, and expose them through properties.

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How create uninstal project?

ersinsivaz16-Aug-06 21:49

ersinsivaz

16-Aug-06 21:49

I can't create uninstal project in my .NET 2003 Setup and Deployment Project. How can I do it?
Thank you for your help...

This is my sign

Re: How create uninstal project?

Nader Elshehabi17-Aug-06 1:49

17-Aug-06 1:49

Hello

Wait a minute!! I thought setp program does that for you?!! Check the Add/Remove programs in the control panel after you install your app. Otherwise why would you make a setup?!!!

Regards Rose | [Rose]

Server Image Path

nachisaravanan16-Aug-06 21:45

nachisaravanan

16-Aug-06 21:45

I am displaying images in my application. I want to display the images dynamically by assigning absolute path to the image controls. When i deploy my application in the web server, i could'nt view the images in the browser since it checks for the clients local path. How to solve this.

Thanks in advance.
Saravanan. P

Christian Graus16-Aug-06 21:47

16-Aug-06 21:47

This is a web app ? If so, how are you managing to load images locally ? If not, how are you loading them and how does the server fit in ?

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

nachisaravanan16-Aug-06 22:26

nachisaravanan

16-Aug-06 22:26

Thanks for immediate reply.it is web app developed using c#.i am dynamically assigning the absolute image path ( like c:/bat.gif ) to image controls at runtime.after depolying, my app is searching for bat.gif in client machine but i want my app to search for bat.gif in server machine and display it.How can i do it.

Christian Graus16-Aug-06 22:35

16-Aug-06 22:35

You need to point to the images using the path to the server, such as www.mysite.com/images/img.gif. If you put a local path, then you'll get a local path.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog

Guffa16-Aug-06 22:19

Guffa

16-Aug-06 22:19

Any images that you want to display have to be accessible through the web server. You have to use the virtual address of the image, not the physical address, as the browser will be getting the image through the web server, not through the file system.

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