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Hello!
I'm stuck with the following problem:
I've created a base class
<br />
public abstract class GenericFieldBase<><br />
from which I derived a number of child classes such as
<br />
public class StringField : GenericFieldBase<string>;<br />
public class IntegerField : GenericFieldBase<int>;<br />
public class DoubleField : GenericFieldBase<double>;<br />
public class DateTimeField : GenericFieldBase<DateTime>;<br />
Question is: what type should a variable have to contain either of these derived classes?
<br />
GenericFieldBase<...> var;<br />
<br />
var = new StringField();<br />
var = new DoubleField();<br />
var = new DateTimeField();<br />
thank you very much!!
-- edit: now alle brackets should be in place.
modified on Wednesday, January 23, 2008 10:45:57 AM
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A variable of type GenericFieldBase can contain an instance of any class derived from GenericFieldBase.
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I'm not quite shure whether I understand corretly.
For 'normal' types I know that typing
<br />
BaseClass var = new DerivedFromBaseClass();<br />
is possible.
But when generics come into play I normally have to give a type argument between < > brackets.
Back to the first example: I could write
<br />
GenericFieldBase<string> var_string;<br />
GenericFieldBase<double> var_double;<br />
GenericFieldBase<datetime> var_datetime;<br />
<br />
var_string = new StringField(); <br />
var_double = new DoubleField();<br />
var_datetime = new DateTimeField();<br />
But what I really want is a variable of type GenericBaseField which can hold a derived class of any generic type. But simply typing
<br />
GenericFieldBase var;<br />
var = new StringField()<br />
gives compile error:
"Using the generic type 'generic type' requires 'number' type arguments "
-- edit: corrected missing brackets
modified on Wednesday, January 23, 2008 10:51:27 AM
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The syntax you gave for GenericFieldBase looked non-generic because there were no angle brackets <> in the declaration. A specific example would clarify your situation.
If C# won't let you derive a class from a generic, you can define a non-generic base class that has a generic member. This may give you the flexibility you need because the derived classes can then use the generic member in different ways.
As a last resort, you can use type "object", which can hold anything. (Sort of like a void pointer in C++).
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Unless I'm missing something in your post - GenericFieldBase isn't actually a generic class. Therefore, you could simply do this:
GenericFieldBase var = new StringField();
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It appears not all your '<' and '>' characters got posted correctly. See if you can edit your post so they are all visble.
led mike
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You have to make a non generic base or interface to handle this.
eg:
public abstract class GenericFieldBase<T> : FieldBase
and then you put all the non generic methods , eg object GetValue() into the nongeneric base
FieldBase var = new StringField();
However, this will most likely defeat the purpose of what you are trying to do, I guess that you are trying to avoid boxing.
So there really isnt any good way to accomplish this.
simply because you cannot assign a concrete implementation of your genericfieldbase to the template "genericfieldbase"
GenericFieldBase<string> will become a separate concrete class in runtime that inherits object , not inheriting your generic base.
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ok,
that puts me back to the drawing board. Thank you very much for your advice.
It nevertheless feels a bit strange. Is it really intended to behave like this? I mean: isn't this a bit of a flaw? After all it limits the usefulness of generics.
whatever.
Thank you very much for your advice.
Arne
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ArneKruger wrote: Is it really intended to behave like this? I mean: isn't this a bit of a flaw? After all it limits the usefulness of generics.
No, you are wrong. Generics is about strong typing[^]. The intention of your original post appears to be the opposite of strong typing as in the case of scripting languages such as Javascript.
led mike
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What you will want to do is open up a FileStream to a specified file, and use a StreamWriter to write to that file. Get the SelectedIndices from your ListView, get the values, seperate them with a comma, and use the Write method on your StreamWriter to write to your file.
I'm going to become rich when I create a device that allows me to punch people in the face over the internet.
"If an Indian asked a programming question in the forest, would it still be urgent?" - John Simmons / outlaw programmer
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John first of all i would like to pay thanks to u that u replied ,
I told u that i m new to c# and i want to write data from list view . can u send me some code about this . when i clik button so the selected items from the list view log into .csv file.
hope u will send me some code .
thanks u so much John.
Tahir
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You might actually want to get his name right. His name is not John - that's the name of a guy in he's quoting in his sig. You might get more of a response if you actually use his right name.
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Using pseudocode:
create a stream file with csv extension;
foreach string s in listviewheaders
stream.write(s+",")
stream.writeline()
foreach listviewitem lvi in listviewitems
{
foreach string s in lvi.Items 'or if you want to check selected items use the SelectedItem property
stream.write(s+",")
stream.writeline()
}
Regards,
Thomas Stockwell
Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Visit my homepage Oracle Studios[ ^]
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thank you Thomas.
I could't understand till now that how i can use this code?
and how i can read each row from list view and write it to csv file?
The Items in the listview are given as :
Name ID Age Phone # Address Salary Job
johny 567 25 1252244 street# 10 19000 programer
Ibrham 78 45 76877 str #67 20000 designer
tony 233 32 3232 str # 32 16888 QualityA
I have rows and columns like this and i wants to write it into .CSV format by clicking on "Create File" button so after doing this the data will be save in csv file as it is in list view.
if you have an idea about this program then write the specific code and tell me that how i can use this code.
thanks.
Tahir
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Hi,
I'm trying to bind a listbox to a object that provides the listbox text:
lineList.DataSource = flatFileMgr;
where flatFileMgr implements IList:
public class FlatFileMgr : IList<string>
I get the following error: "Complex DataBinding accepts as a data source either an IList or an IListSource."
But flatFileMgr IS an IList! This is maddening! Any suggestions?
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I've looked at many examples like this where the datasource is an existing type, like an array. (In fact, as a workaround I'm currently copying ALL the objects to an ArrayList, and using that as the datasource. It's inefficient but it works.)
I haven't seen an example yet of a custom type that implements IList, although the Microsoft documentation claims this should work.
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>>But flatFileMgr IS an IList!
No, your flatFileMgr is an IList[of string] , not an IList
IList is the nongeneric interface.
Make it:
public class FlatFileMgr : IList<string> , IList
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Interesting. So what am I doing wrong? Doesn't a generic require a type? How do I specify a datasource that can provide strings?
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Just saw the rest of your response. Thanks! I'll try it.
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I'm hoping someone can help me out here, I am attempting to Serialize an object which contains a List<class> of another class into XML. However no matter what I try it always produces this:
RootElement
OrganisationXML
Organisation
/Organisation
Organisation
/Organisation
/OrganisationXML
/RootElement
Is there anyway to stop it producing the name of the generic List and just output the items contained in the list,
i.e.
RootElement
Organisation
/Organisation
Organisation
/Organisation
/RootElement
Any ideas would be greatly appreciated....
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RichardContact-1 wrote: However no matter what I try it always produces this:
It appears you have not posted the '<' and '>' correctly. Read the posting guidelines to see how to manage those characters.
led mike
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Hello every one,
After read some articles about WCF, I made some performace test, and in my test the WCF is worst than WS
The first test I have made it the time response, I create 3 services, one is WS and 2 WCF, one with basicHttpBiding(WS standard equivalent) and another with wsHttpBindig(WSE equivalent).
All services return one dataset, I try with 2mb data anda 128k data, in both cases the WS is faster than WCF, faster in comparison basicHttpBinding and aldo wsHttpBinding, in all cases I tested in IIS6 as a host.
http://img132.imageshack.us/img132/6813/wsxwcfmt8.png
Tempo gasto = time elapse
milisegundos = milliseconds
<br />
private void btnNormalWeb_Click(object sender, EventArgs e)<br />
{<br />
DataSet dsReturn;<br />
DateTime d1, d2;<br />
wsTeste.wsTeste objwsTeste = new wsTeste.wsTeste();<br />
<br />
d1 = DateTime.Now;<br />
dsReturn = objwsTeste.Retorno();<br />
d2 = DateTime.Now;<br />
lblTempoExecucaoWS.Text = string.Format("Tempo Gasto Normal: {0} milisegundos", (d2 - d1).TotalMilliseconds);<br />
}<br />
<br />
private void btnNormalWCF_Click(object sender, EventArgs e)<br />
{<br />
DataSet dsReturn;<br />
DateTime d1, d2;<br />
wcfServiceBasic.WCFServiceClient objwcfTeste = new wcfServiceBasic.WCFServiceClient();<br />
<br />
d1 = DateTime.Now;<br />
dsReturn = objwcfTeste.Retorno(); <br />
d2 = DateTime.Now;<br />
lblTempoExecucaoWCFBasic.Text = string.Format("Tempo Gasto Basic: {0} milisegundos", (d2 - d1).TotalMilliseconds); <br />
}<br />
<br />
private void btnNormalWCFWSE_Click(object sender, EventArgs e)<br />
{<br />
DataSet dsReturn;<br />
DateTime d1, d2;<br />
wcfServiceWSE.WCFServiceClient objwcfTeste = new wcfServiceWSE.WCFServiceClient();<br />
<br />
d1 = DateTime.Now;<br />
dsReturn = objwcfTeste.Retorno();<br />
d2 = DateTime.Now;<br />
lblTempoExecucaoWCFWSE.Text = string.Format("Tempo Gasto WSE: {0} milisegundos", (d2 - d1).TotalMilliseconds);<br />
}<br />;
Some one know why the WCF im my case are not fast enough WS.
Sorry by English!
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hi;
I wanna create new items acording to database .i add them in a panel but cant access data which user select.How can i acces it?i wanna take all data whit 1 button click as well
<br />
<br />
<br />
void opencon()<br />
{<br />
con= new OleDbConnection("Provider=Microsoft.Jet.Oledb.4.0;Data Source=" +<br />
Server.MapPath("db/xxx.mdb"));<br />
<br />
}<br />
<br />
void objeckcreate()<br />
{<br />
...get values and items for exp. shows=1 dropdown its goes to nuber of data <br />
<br />
<br />
<br />
if (shows== 1)<br />
{<br />
....use literal to make see good:D<br />
Literal ltr2 = new Literal();<br />
ltr2.Text = "its work "<br />
Panel1.Controls.Add(ltr2);<br />
<br />
Label basdrop= new Label();<br />
nameofshow.ID = "nameshow" + nameshowdatavalue;<br />
nameofshow.Text=nameobject;<br />
Panel1.Controls.Add(nameofshow);<br />
<br />
DropDownList Mydrop= new DropDownList();<br />
Mydrop.ID = "Mydrop" + namedatavalue;<br />
<br />
<br />
con.Open();<br />
...fill whit dataset dropdowns<br />
<br />
Mydrop.DataSource = xdataset.Tables["xlol"];<br />
Mydrop.DataTextField ="namefield";<br />
Mydrop.DataValueField = "namevalue";<br />
Mydrop.DataBind();<br />
Mydrop.Width=100;<br />
con.Close();<br />
Mydrop.Items.Insert(0, "--Choose--");<br />
Mydrop.AutoPostBack = true;<br />
<br />
<br />
dropportfoyekle.SelectedIndexChanged += new EventHandler(deneme_SelectedIndexChanged);<br />
...i try put 1 static dropdown and use its spec but cant work cause them not public:(<br />
<br />
Panel1.Controls.Add(dropportfoyekle);<br />
<br />
<br />
}<br />
<br />
<br />
}<br />
protected void Page_Load(object sender, EventArgs e)<br />
{<br />
opencon();<br />
if (!this.Page.IsPostBack)<br />
{<br />
<br />
objeckcreate();<br />
}<br />
}<br />
protected void button_Click(object sender, EventArgs e)<br />
{<br />
<br />
how can i takeee<br />
}<br />
<br />
<br />
ty
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