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Is there a way using .NET Generics of providing a C# equivalent to the following C++?
<pre>
#include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
using namespace std;
class Employee
{
public:
Employee(int id, const string& name) : _id(id), _name(name) {}
int id() const { return _id; }
string name() const { return _name; }
private:
int _id;
string _name;
};
// Employees are equal if they share the same name.
class EmployeeEqualTo
{
public:
EmployeeEqualTo(string name) : _name(name) {}
bool operator()(const Employee& employee) const
{ return employee.name() == _name; }
private:
string _name;
};
void Run()
{
vector<Employee> employees;
employees.push_back(Employee(1, "Peter"));
employees.push_back(Employee(2, "Paul"));
employees.push_back(Employee(3, "Helen"));
vector<Employee>::const_iterator it;
string match;
// Find Paul
match = "Paul";
it = find_if(employees.begin(), employees.end(), EmployeeEqualTo(match));
cout << "Name: " << it->name() << ", id: " << it->id() << "\n";
// Find Helen
match = "Helen";
it = find_if(employees.begin(), employees.end(), EmployeeEqualTo(match));
cout << "Name: " << it->name() << ", id: " << it->id() << "\n";
}
int _tmain(int argc, _TCHAR* argv[])
{
Run();
return 0;
}
</pre>
The key thing here is that we just need to define a single function object EmployeeEqualTo to find an employee that is equal to a match that we specify.
Now consider a C# generics attempt.
<pre>
class Employee
{
public Employee(int id, string name)
{
_id = id;
_name = name;
}
private int _id;
public int ID
{
get { return _id; }
}
private string _name;
public string Name
{
get { return _name; }
}
}
class EmployeeTester
{
public void Run()
{
List<Employee> employees = new List<Employee>();
employees.Add(new Employee(1, "Peter"));
employees.Add(new Employee(2, "Paul"));
employees.Add(new Employee(3, "Helen"));
Employee employee;
// Find Paul
employee = employees.Find(EmployeeEqualToPaul);
Console.WriteLine("Name = {0}, ID = {1}", employee.Name, employee.ID);
// Find Helen
employee = employees.Find(EmployeeEqualToHelen);
Console.WriteLine("Name = {0}, ID = {1}", employee.Name, employee.ID);
}
/// <summary>
/// Is employee Paul?
/// </summary>
private bool EmployeeEqualToPaul(Employee employee)
{
return employee.Name == "Paul";
}
/// <summary>
/// Is employee Helen?
/// </summary>
private bool EmployeeEqualToHelen(Employee employee)
{
return employee.Name == "Helen";
}
}
</pre>
We have to define two predicates, EmployeeEqualToPaul and EmployeeEqualToHelen to provide the same functionality. Is there a way of defining a single predicate in this case?
Kevin
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Hi Kevin!
Just like you used a separate class to host the predicate in the C++ case, you can do the same in C#.
For example:
class EmployeeComparer
{
public static string Name;
public static bool Compare(Employee e)
{
return e.Name == Name;
}
}and then
EmployeeComparer.Name = "Helen";
employee = employees.Find(EmployeeComparer.Compare); will give you the employee with the given name.
Regards,
mav
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Yep. That looks fine. I'd sort of thought have something similar, but having that as part of the Employee class. Yours is neater though. 
Kevin
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i've a database with this structure:
[Name]* = text
[Surname]*= text
[Address]= text
[Description] = text
[Note]= memo
[Image] = OLE OBJECT
[Number] = int32
string query = "INSERT INTO TableInformation ([Name], [Surname], [Address], [Description], [Note], [Image], [Attached], [Number]) VALUES('";
conn.Open();
OleDbCommand cmd = new OleDbCommand();
// getName(), getSurname(), getAddress() return string
query += getName() + "', ";
query += getSurname() + ", '";
if(getAddress() != "")
query += "'" + getAddress() + "', ";
else
query += DBNull.Value + ", ";
// getMemo() return string
if(getMemo() != "")
query += "'" + getMemo() + "', ";
else
query += DBNull.Value + ", ";
query += "@Image, ";
// image is byte[]
if(image != null){
cmd.Parameters.Add("@Image", OleDbType.VarBinary, (int)image.Length).Value = image;
}
else
cmd.Parameters.Add("@Image", DBNull.Value);
}
if(getValue() != "")
query += "'" + getValue();
else
query += DBNull.Value;
query += ")";
cmd.Connection = conn;
cmd.CommandText = query;
cmd.ExecuteNonQuery();
the query when image is null is like this:
---------------------------
INSERT INTO TableInformation ([Name], [Surname], [Address], [Description], [Note], [Image]) VALUES('Sasuko', 'Divos', 'green street', 'It is good', , @Image, )
but i get a INSERT INTO error, why?
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For security's sake you already know how to do parameters. Make ALL the values being inserted in to parameters!
ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell
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really no, can u explain?
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Sasuko wrote: cmd.Parameters.Add("@Image", OleDbType.VarBinary, (int)image.Length).Value = image;
}
You did this for image column - Do it for all the other values as well. This will improve the security of your application and assist in reducing the ability of a mallicious attacker getting to your database via your web application. For more information read: SQL Injection Attacks and some tips on how to prevent them[^]
I can understand someone who does not know about parameters not using them, but it is obvious you know how to add a parameter to the commnand (as you demonstrated it in your code). It seems strange to use parameters for some values but not others.
ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell
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Because the fifth and sevent values are missing.
You can't put a DBNull value into a string, you have to add the text "null" to the string.
---
b { font-weight: normal; }
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Thanks at all you guys!
How can i protect my password for connection to the Microsoft Access Database?
Can i use Store Procedure with Access Database?
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Hi,
How can i use variables as an old value an dnew value in String variable's Replace method like Replace(var1, var2). I tried it but it is not working.
p
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sohne wrote: How can i use variables as an old value an dnew value in String variable's Replace method like Replace(var1, var2).
Like this:
string originalString = "I like cats.";
string oldValue = "cats";
string newValue = "dogs";
string newString = originalString.Replace(oldValue, newValue);
ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell
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Hello!
I would like to import conactinformation to Microsoft Outlook C#. I know how to do this if you want the information to be put into your regular contactlist in Microsoft Outlook. But I can't get it to be a part of "Public Folders -> All Public Folders". Here is my code:
<br />
public void exportContactToOutlook(Person contact)<br />
{<br />
Outlook.Application objOutlook = new Outlook.ApplicationClass();<br />
NameSpace outlookNS = objOutlook.GetNamespace("MAPI");<br />
MAPIFolder contactFolder = outlookNS.GetDefaultFolder(OlDefaultFolders.olPublicFoldersAllPublicFolders);<br />
<br />
<br />
Outlook.ContactItem objContact = (Outlook.ContactItem)objOutlook.CreateItem(Outlook.OlItemType.olContactItem); <br />
objContact.CompanyName = contact.CompanyName;<br />
objContact.Save();<br />
}<br />
This will only save it to the regular contactlist. I know that this code shouldn't work but what is the missing link? Any ideas?
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How can be a transparent panel control can be created. As I tried in many ways but it is applicable to window but not to the required control (panel), as well as I also have observed that Transparency will be applicable to windows forms but not to user control. Is it so, if yes why.
Shashidhar
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i have tried a lot but did not find any method for that
i think it's impossible
Regards,
Pramod
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Try making a bitmap that is all one colour and setting it as the background image for your panel.
Then add the following code to the form_Load event
Bitmap bitmap = (Bitmap)pnlBackground.BackgroundImage;
bitmap.MakeTransparent(bitmap.GetPixel(1, 1));
TransparencyKey = BackColor;
You may also need to start the form minimized and then do WindowState = FormWindowState.Normal; I don't know why but sometimes this is the case.
Cheers
Kev
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Hello,
can anyone show me a sample how to establish a GPRS connection in c# .net?
Or tell me where to look.
thanks
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Hi,
How to start and stop windows services using c# asp.net.
Thanks
Warm Regards
Prakash-B
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You can use the System.ServiceProcess.ServiceController class, from the System.ServiceProcess.dll assembly.
Bear in mind that you generally need administrative privileges to stop or start a service, which your ASP.NET code will not normally have. You'll typically have to change the user that the code runs under. On Windows 2000 or Windows XP, you configure this with the <processModel> element in the Machine.config file, and it affects all ASP.NET applications on the server; on Windows Server 2003 you configure it through the Internet Information Services administration console, all applications in the same application pool share the same worker process.
Stability. What an interesting concept. -- Chris Maunder
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I am reading a file into a listBox as follows:
***********************************
StreamReader SR;
FileStream FS = File.Open("c:\\wsIder\\info.ini", FileMode.Open, FileAccess.Read);
SR = new StreamReader(FS);
string line;
while((line = SR.ReadLine()) != null)
{
viewS.Items.Add(line);
}
SR.Close();
******************************
the file contains section separated with bracket like this
[SEC1]
...some text
[SEC2]
...some text
etc
When I display the file in the listbox, I would like to use colored text for the sections. [SEC1]=red, {sec2]=green..etc
Any idea how to do this?
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With the standard listbox control, you cannot do that. You need a owner drawn listbox. See this article: this is probably what you need:
http://www.codeproject.com/cs/combobox/colorlistbox.asp[^]
Once you have implemented the listbox as described in the article, you just have to do some parsing of the text you read from the file, like if the line starts with a '[' then change that item's color to red... etc etc
Koushik Biswas
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Hi
i am working in c# with infragistics
In c# windows applicaion, I will be passing data from textbox..such that
for example:i ahev 3 texboxes labeled
name:
age:
salary:....
Now name is the parent and age and salary r the child..so if i pass data in
the appropriate textbox..It should be added in the [B]ultrawintree..[/B]such that
name(parent) should show up on the root node of the tree. and age and
salary(child) should show up under the root node.
as I am new to infragistics , I am learning. Please help me with
coding..and please explain me ...
dhol
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What is infragistics, a class library ? You need to ask them.
Christian Graus - Microsoft MVP - C++
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I have 2 classes and I want when the second class raises an event, the first class can catch and do something.
I have heard about using delegate to do this, but I dont know how to do?
Hung
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This[^] is where you should begin. The documentation actually explains things pretty well.
"we must lose precision to make significant statements about complex systems."
-deKorvin on uncertainty
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