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Is there an "approved" means of recursing an anonymous method, I spent most Sunday reading the C# language spec and other resources, and couldn't see anything. Recursion is one of the more common reasons for me writing a method that is only referenced once, so anonymizing them is attractive.
The only means I could devise was to have the method grab itself off the stack and use MethodBase Invoke to invoke itself eg
new StackTrace().GetFrame(0).GetMethod().Invoke(newTarget)
It works, but it's not pretty - Ta PhilD
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What you're asking is how to invoke anonymous methods outside of the block they were defined in.
I think that's a bad idea. Anonymous methods really aren't designed for this; as you've discovered, it's not easy calling the anonymous method outside of the block that defined the method.
If you absolutely must do this, the easiest way would be to do something like:
System.Reflection.MethodInfo.GetCurrentMethod().Invoke
But that's ugly, not to mention horribly inefficient -- reflection is always much slower than calling code statically. I recommend you don't use anonymous methods this way.
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Is it only a bad idea because the only way to do it is "ugly", or do you have a philosophical objection to the principle - ie if there was a language reserved word such as "self" (sorry SmallTalk) which enabled one to write
"self(arg1, arg2);"
would you still say it was a bad idea?
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No, not only because it is ugly and slow, but also because it is getting beyond the scope of purpose for anonymous methods, IMO. When it comes down to it, anonymous methods aren't meant to be called from anywhere other than the method defining the anonymous method.
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Respectively I have to disagree. Recursion is a natural feature of C# and should be universally available in all methods. A case in point being property accessors, there is nothing to prevent a property accessor method recursing, usually erroneously. And, if an anon method calls itself it is surely, by definition, being done within the scope of the method in which its contained.
rgds phild
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I'm not commenting on whether or not recursion should be allowed in anonymous methods, I'm speculating on the current state of things, which is that anonymous methods are not meant to be directly called from anywhere but the defining function, hence being "anonymous".
If you feel very strongly about making them callable elsewhere, you could give the C# language team some feedback indicating this on sites like connect.microsoft.com, or on the MSDN blogs of the C# language devs, they always welcome feedback.
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Recursion is not just one method calling itself. To introduce a way for a method to anonymously call itself would only be usabale for self recursion, but not for mutual recursion. As it would only allow one special case of recursion, it would not make recursion universally available, it would only make that special case of recursion universally available.
I don't think that it would be a good idea to introduce such a construct, as it would work towards reducing the concept of recursion into just self recursion.
---
b { font-weight: normal; }
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There's nothing to prevent an anon method calling an external method which in turn calls the method in which the anon method resides, which duly invokes the anon method - voila indirect recursion.
as for defining recursion - the existence of multiple instances of the gizmo (method, function, entry point whatever) on the stack - would be where i'd start; it being the means by which my NoRecursion attribute detects undesirable recursions.
Which reminds me that I haven't tried giving an anon method any attributes, yet;)
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pjd1001 wrote: There's nothing to prevent an anon method calling an external method which in turn calls the method in which the anon method resides, which duly invokes the anon method - voila indirect recursion.
No, it's not indirect recursion. The anonymous method only calls a recursive method, it has no part of the recursion itself.
---
It's amazing to see how much work some people will go through just to avoid a little bit of work.
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public someClass
{
public double methodOne(int arg1, List<double> arg2)
{
float number = Math.Sqrt(arg1)
double answer;
arg2.ForEach(delegate{double itemVal)
{
answer += (arg1 < 0) ? extClass.Meth1(this, itemVal, arg1) : extClass.Meth2(this. itemVal, arg1);
}
}
}
public class extClass
{
public double Meth1(someClass mySomeClass, double value, int order)
{
blah blah
double var = mySomeClass.MethodOne(myInt, myListDoubles)
}
}
Surely there is some sort of recursion happening here. I call it indirect recursion - as a result of MethodOne being indirectly recursed then so too is the Action delegate within MethodOne. If I wanted to prevent this I would have MethodOne examine the stack to determine if it, itself, has a prior entry and to react accordingly (it might raise an Exception or simply return zero). If I did not detect recursion and do something about it at the top of the method then I say that MethodOne, including the anon methods therein, are in a state of recursion.
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Yes, there is indirect recursion, and there is an anonymous method, but they are independent of each other. The anonymous method is not an integral part of the recursion. If the Meth1 method would have called the anonymous method, it would have been.
---
It's amazing to see how much work some people will go through just to avoid a little bit of work.
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point taken - how about consequential recursion;P
the stack interrogation method works fine, and I've generalised it into a static method, so the code in the anon method looks reasonable ie within a directory related anon method it would look something like utils.RecurseMe(directory, includeReparsePoints) - RecurseMe's currently only handles void methods, when I need it I'll do a generic version to handle return values.
today public static void RecurseMe(params object[] methodParams);
tomorrow public static void RecurseMe<retType>(params object[] methodParams) where retType:class;
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To define recursion, we must first define recursion!!
All generalizations are wrong, including this one!
(\ /)
(O.o)
(><)
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pjd, did you figure out how to do this? It looks like you can do it by first assigning it to null:
Function f = null;
f = delegate() { f(); }
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Judah,
thanks I've filed that away for future reference - can't recall the context in which I wanted to do it now - probably a predicate method.
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This sounds like a C++ question. Are you sure you're in the right forum?
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I am using a commercial grid to display my data. I don't have any problem to display the whole table to the grid. For instance, the following code displays a whole table to the grid.
<br />
grid1.SetDataBinding(table1BindingSource);<br />
Now, I only want to display the FirstName and the LastName
I have the following in my form
table1BindingSource and db1DataSet
From db1DataSet, I can see the following by intellicense; my table names Tabl1
from intellicense I can see
Table1.FirstNameColumn and Table1.LastNameColumn;
My question, how can I use table1BindingSource and db1DataSet to display only the firstname and the lastname rather than the whole table?
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You could use the Query Builder. Assuming you are using C# Express Edition, this "in-built" help page from the C# help file that installs with the C# express edition will show you how. There are also related help pages you might like to read! There are other ways to achieve the desired result but for a novice, this might be the easiest way.
ms-help://MS.VSExpressCC.v80/MS.NETFramework.v20.en/dv_vdt01/html/815a30ce-6fb1-4611-bf43-bedd2020c443.htm
Although you are wanting to program in C#, the question is about database. Try posting database questions in the correct forum.
modified 1-Aug-19 21:02pm.
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Try this link.
All generalizations are wrong, including this one!
(\ /)
(O.o)
(><)
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Hey guys
i have a c# project and ive added a project installer...
is there any way i can install some fonts to in the windows font directory as the application gets installed?
many thanks
Will
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Checkout the help of the Visual Studios...
It is all in there ... 
Don't you also love the code?
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ive had a dig around and cant much :S
can u point me in the right direction?
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When you have created a new setup project in vs2005, you go to the 'File System' right click on 'File System on Target Machine', 'Add Special Folder', 'Fonts Folder'.
And then you just add in the Fonts folder the right files...
Just of topic... I have helped you could you help me? I want to finish my work (General Discussion - Cards?).
Don't you also love the code?
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thanks dude! spot on!! 
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hi every one,
well I have this little problem here. I'm getting a nullreferenceException when I try to access the value of a DataGridViewComboBox column. I have correctly bounded the column and its also showing the values of that table too. The name of the column is "AttendanceComboBoxColumn". now I just wanna know how to get the value selected in this comboBox.
for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
//MessageBox.Show("att: " + dataGridView1["AttendanceComboBoxColumn", i].Value.ToString() + "\n empid: " + dataGridView1["empIDDataGridViewTextBoxColumn", i].Value.ToString()+"\nDate: "+selected_date.ToString());
//MessageBox.Show("att: " + dataGridView1["AttendanceComboBoxColumn", i].Value.ToString() + "\n empid: " + dataGridView1["empIDDataGridViewTextBoxColumn", i].Value.ToString());
//MessageBox.Show("att: " + dataGridView1["AttendanceComboBoxColumn", i].Value.ToString() );// null ref
//MessageBox.Show("att: " + dataGridView1["empIDDataGridViewTextBoxColumn", i].Value.ToString()); // ok
//sqlUpdateCommandAttendance.Parameters["@AttendanceID"].Value = Convert.ToDecimal(dataGridView1["AttendanceComboBoxColumn", i].Value);
int c = AttendanceComboBoxColumn.DisplayIndex;
MessageBox.Show(dataGridView1[c, i].Value.ToString());
sqlUpdateCommandAttendance.Parameters["@AttendanceID"].Value = Convert.ToDecimal(dataGridView1[c,i].Value);
sqlUpdateCommandAttendance.Parameters["@original_empid"].Value = Convert.ToDecimal(dataGridView1["empIDDataGridViewTextBoxColumn", i].Value);
sqlUpdateCommandAttendance.Parameters["@original_attendDate"].Value = selected_date;
count+=sqlUpdateCommandAttendance.ExecuteNonQuery();
}
thanks in advance
Rocky
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