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Is it possible to define an attribute that describes a property of a class at runtime?
For example, you have a class called "employee", and it has a property "name". The "name" property has an attribute that tells any calling code whether or not this property is "writable" and/or "readable", even though this property has both get/set accessors.
Maybe there is another way to do this, and I just don't have enough experience.
Any help is appreciated.
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For what you are trying to do, I suggest that you should try to avoid using attributes
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Is there a way to set a property of a property, at runtime, then?
This is what I REALLY want to do, but I believe this is not possible:
<br />
<br />
<br />
[AttributeUsage(AttributeTarget.Property,Inherited=true,AllowMultiple=true)]<br />
public class SecurityInfoAttribute : Attribute<br />
{<br />
private int readable;<br />
private int writable;<br />
<br />
<br />
public SecurityInfoAttribute(int readable, int writable)<br />
{<br />
this.security_readable = 0;<br />
this.security_writable = 0;<br />
<br />
}<br />
<br />
public int Readable<br />
{<br />
get<br />
{<br />
return readable;<br />
}<br />
set<br />
{<br />
readable = value;<br />
}<br />
}<br />
<br />
public int Writable<br />
{<br />
get<br />
{<br />
return writable;<br />
}<br />
set<br />
{<br />
writable = value;<br />
}<br />
}<br />
<br />
<br />
}<br />
<br />
<br />
<br />
public class employee {<br />
<br />
string name;<br />
[SecurityInfo(getReadSecurityInfo(userId), getWriteSecurityInfo(userId))]<br />
string Name{get{return name;}set{name = value;}}<br />
<br />
<br />
<br />
} <br />
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I have a form which has a DataGrid which I bind to an ArrayList. The grid
displays fine and I can edit the values on the grid and they get passed on
to the objects in the ArrayList itself. The problem, however, is with
handling adding and remove objects from the ArrayList. It doesn't
automatically update the DataGrid to reflect the changes to the ArrayList.
So I tried this, which kind of works  :
private void btnNew_Click(object sender, System.EventArgs e)
{
myAL.Add(new myClass());
MyGrid.DataSource = null;
MyGrid.DataSource = myAL;
}
private void btnDel_Click(object sender, System.EventArgs e)
{
myAL.Remove(myAL[MyGrid.CurrentRowIndex]);
MyGrid.CurrentRowIndex = 0;
MyGrid.DataSource = null;
MyGrid.DataSource = myAL;
}
This works until you try to either: remove the bottom item on the grid
(System.ArgumentOutOfRangeException) or add an item to an empty grid
(System.IndexOutOfRangeException). Plus it just doesn't seem like the right
way to do this. Can anybody help me out here and point me in the right
direction? Everything I've found online so far covers binding a grid to a
datatable or dataview only.
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Why not bind to a dataset instead? Not sure it is the best method but if you want to stay with ArrayList try rebinding the datagrid, should "refresh" it.
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Actually, this is correct behavior, though not always desired.
Also, remember that the DataGrid acts no differently when binding to various data sources, like DataSet, DataTable, ArrayList, etc. If you look at the DataGrid's DataSource property, you'll see that it takes an Object that implements either IListSource, IList, or IEnumerable. It doesn't care much about the actual type.
So, any of those examples you've seen for other types will apply to the ArrayList.
One such method would be to get the CurrencyManager from the BindingContext of the DataGrid. You can receive event notification when the list changes and update the DataGrid either manually or by reassigning the list to the DataGrid.DataSource property (ps, you don't need to set it to null first).
-----BEGIN GEEK CODE BLOCK-----
Version: 3.21
GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++
-----END GEEK CODE BLOCK-----
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Take some standard code such as shown below. It simply loops to add up a
series of terms and it produces the correct result.
// sum numbers with a loop
public int DoSumLooping(int iterations)
{
int result = 0;
for(int i = 1;i <=iterations;i++)
{
result += i;
}
return result;
}
Now translate this into a specific solution that doesn't use looping (and
use the same value for the number of iterations the loop performs). This
code returns an incorrect result. The method consists entirely of a very
straightforward code statement, but in this case .NET adds the numbers
incorrectly.
public double ComputeSum( )
{
// Brute force sum method
// For iterations == 10000
double sum = 0+ 1+ 2+ 3+ 4+ 5+ 6+ 7+ 8+ 9+ 10+ 11+ 12+ 13+ 14+ 15+ ...
+ 9997+ 9998+ 9999+ 10000;
return sum;
}
The above method returns an incorrect result with any number of terms above
about 200. It will correctly add 1 + 2 + ... + 200, but it will NOT
correctly add 1 + 2 + ... + 1000.
I have just run across this, and I have not yet researched the possible
reasons for this behavior. It may be a known issue related to either stack
size or the length of a code line, but to my knowledge it hasn't been
discussed in any of the "popular" literature on C# and .NET. I need to write
code like this, so if anyone has already encountered this issue, please
advise me.
Here's another example that also creates problems, but of a somewhat
different nature. Take the following code and translate it into a specific,
non-looping method and try to execute it using reflection. It fails.
public double LoopToCompute()
{
double sumOfProducts = 0;
double grandTotal = 0;
for (int i = 0; i < maxRows; ++i)
{
for (int j = 0; j < maxCols; ++j)
{
sumOfProducts += coeff[j] * table[i][j];
}
a_point[i] = sumOfProducts;
grandTotal += sumOfProducts;
sumOfProducts = 0;
}
return grandTotal;
}//LoopToCompute
The above code works -- but it's equivalent code with loops unrolled (shown
below) doesn't work unless the maxRows is set very small. For small values,
the 2 methods (above and below) produce identical results. There is nothing
"wrong" with the code in that sense. It's similar to the above situation. If
the "size" of the code statement or the number of code statements is too
large, .NET fails. In this case (using reflection) it doesn't return the
incorrect result, as the first example did. In this case, reflection calls
it an invalid program and refuses to run it (but only when the value of
maxRows is above about 250). The reason for this is probably
straightforward. However, I have the need to make statements like this for
performance reasons so I need a work-around. Any suggestions are
appreciated! All comments are appreciated.
public double DoBruteForceCompute()
{
double bruteForceSum = 0;
point1=coeff1*table[0][0] +coeff2*table[0][1] +coeff3*table[0][2]
+coeff4*table[0][3] +coeff5*table[0][4] +coeff6*table[0][5]
+coeff7*table[0][6] +coeff8*table[0][7] +coeff9*table[0][8]
+coeff10*table[0][9] +coeff11*table[0][10] +coeff12*table[0][11]
+coeff13*table[0][12] +coeff14*table[0][13] +coeff15*table[0][14]
+coeff16*table[0][15] +coeff17*table[0][16] +coeff18*table[0][17]
+coeff19*table[0][18] +coeff20*table[0][19] +coeff21*table[0][20]
+coeff22*table[0][21] +coeff23*table[0][22] +coeff24*table[0][23]
+coeff25*table[0][24] +coeff26*table[0][25] +coeff27*table[0][26]
+coeff28*table[0][27] +coeff29*table[0][28] +coeff30*table[0][29]
+coeff31*table[0][30] +coeff32*table[0][31] +coeff33*table[0][32]
+coeff34*table[0][33] +coeff35*table[0][34] ;
point2=coeff1*table[1][0] +coeff2*table[1][1] +coeff3*table[1][2]
+coeff4*table[1][3] +coeff5*table[1][4] +coeff6*table[1][5]
+coeff7*table[1][6] +coeff8*table[1][7] +coeff9*table[1][8]
+coeff10*table[1][9] +coeff11*table[1][10] +coeff12*table[1][11]
+coeff13*table[1][12] +coeff14*table[1][13] +coeff15*table[1][14]
+coeff16*table[1][15] +coeff17*table[1][16] +coeff18*table[1][17]
+coeff19*table[1][18] +coeff20*table[1][19] +coeff21*table[1][20]
+coeff22*table[1][21] +coeff23*table[1][22] +coeff24*table[1][23]
+coeff25*table[1][24] +coeff26*table[1][25] +coeff27*table[1][26]
+coeff28*table[1][27] +coeff29*table[1][28] +coeff30*table[1][29]
+coeff31*table[1][30] +coeff32*table[1][31] +coeff33*table[1][32]
+coeff34*table[1][33] +coeff35*table[1][34] ;
[...]
point500=coeff1*table[499][0] +coeff2*table[499][1] +coeff3*table[499][2]
+coeff4*table[499][3] +coeff5*table[499][4] +coeff6*table[499][5]
+coeff7*table[499][6] +coeff8*table[499][7] +coeff9*table[499][8]
+coeff10*table[499][9] +coeff11*table[499][10] +coeff12*table[499][11]
+coeff13*table[499][12] +coeff14*table[499][13] +coeff15*table[499][14]
+coeff16*table[499][15] +coeff17*table[499][16] +coeff18*table[499][17]
+coeff19*table[499][18] +coeff20*table[499][19] +coeff21*table[499][20]
+coeff22*table[499][21] +coeff23*table[499][22] +coeff24*table[499][23]
+coeff25*table[499][24] +coeff26*table[499][25] +coeff27*table[499][26]
+coeff28*table[499][27] +coeff29*table[499][28] +coeff30*table[499][29]
+coeff31*table[499][30] +coeff32*table[499][31] +coeff33*table[499][32]
+coeff34*table[499][33] +coeff35*table[499][34] ;
bruteForceSum =
point1 +
point2 + ... +
point499 +
point500
;
return bruteForceSum;
}//DoBruteForceCompute
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I'd suggest you to use ILDASM and see the generated code. This will help to isolate if the problem is on JIT or on C# compiler. Also, you could try using other .NET languages, like VB.NET.
BTW, for this kind of code, managed C++ rules. With C++ you always have much more control over the compiler.
Help me dominate the world - click this link and my army will grow
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Interesting situation 
What version of .NET are u using? Are you going over the 2048 character line limit?
The did the same thing, but with a single " + xxxx" on a single line and get the proper result (50005000 for 10000). In fact the compiler does constant folding and only loads the result.
leppie::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.
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I found the problem. I think you could have guessed it -- it was related to the line limit. Here's what I was doing. I was using code to generate my unrolled loop code. I was then compiling this in a process and using reflection to load the assembly and invoke the method.
I was not getting any compiler errors, nor was I getting any runtime errors. I was just getting incorrect math results.
However, when I posted the code (without the reflection part) everyone else got the correct results. This prompted me to look at the reflection/compilation code more closely. It turns out the when I pasted the generated code into the IDE I discovered the line limit you mentioned.
I inserted a new line in my generated code after every 200 terms, and presto- the math results were now correct.
It's a bit disconcerting that I didn't get a compiler error from the command line compiler. I don't know why yet. Does the command line compiler have that same line limit? I assume so, given my experience.
I guess the compiler just took as many terms as it could and somehow terminated the statement and produced a runnable program ... all very strange. I wouldn't have thought that possible.
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It's working with DotGNU anyway ... Log a bug with MS
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leppie,
Do you happen to know why the following method "is not a valid program"? It compiles fine, but the runtime won't even try to run it. It contains 500 statements (I cut out 497 of them for this post) like those below. The method represents another unrolled loop. (And this is the one I mentioned that is actually 5-10 times slower than the loop after it's unrolled.) I appreciate any comments.
Dave
P.S. I forgot to mention that the problem is related to the number of statements in the method. 1000 doesn't work. I think it works up to a few hundred statements, then stops being "a valid program."
public double DoBruteForceCompute()
{
double bruteForceSum = 0;
point1=coeff1*table[0][0] +coeff2*table[0][1] +coeff3*table[0][2]
+coeff4*table[0][3] +coeff5*table[0][4] +coeff6*table[0][5]
+coeff7*table[0][6] +coeff8*table[0][7] +coeff9*table[0][8]
+coeff10*table[0][9] +coeff11*table[0][10] +coeff12*table[0][11]
+coeff13*table[0][12] +coeff14*table[0][13] +coeff15*table[0][14]
+coeff16*table[0][15] +coeff17*table[0][16] +coeff18*table[0][17]
+coeff19*table[0][18] +coeff20*table[0][19] +coeff21*table[0][20]
+coeff22*table[0][21] +coeff23*table[0][22] +coeff24*table[0][23]
+coeff25*table[0][24] +coeff26*table[0][25] +coeff27*table[0][26]
+coeff28*table[0][27] +coeff29*table[0][28] +coeff30*table[0][29]
+coeff31*table[0][30] +coeff32*table[0][31] +coeff33*table[0][32]
+coeff34*table[0][33] +coeff35*table[0][34] ;
point2=coeff1*table[1][0] +coeff2*table[1][1] +coeff3*table[1][2]
+coeff4*table[1][3] +coeff5*table[1][4] +coeff6*table[1][5]
+coeff7*table[1][6] +coeff8*table[1][7] +coeff9*table[1][8]
+coeff10*table[1][9] +coeff11*table[1][10] +coeff12*table[1][11]
+coeff13*table[1][12] +coeff14*table[1][13] +coeff15*table[1][14]
+coeff16*table[1][15] +coeff17*table[1][16] +coeff18*table[1][17]
+coeff19*table[1][18] +coeff20*table[1][19] +coeff21*table[1][20]
+coeff22*table[1][21] +coeff23*table[1][22] +coeff24*table[1][23]
+coeff25*table[1][24] +coeff26*table[1][25] +coeff27*table[1][26]
+coeff28*table[1][27] +coeff29*table[1][28] +coeff30*table[1][29]
+coeff31*table[1][30] +coeff32*table[1][31] +coeff33*table[1][32]
+coeff34*table[1][33] +coeff35*table[1][34] ;
[...]
point500=coeff1*table[499][0] +coeff2*table[499][1] +coeff3*table[499][2]
+coeff4*table[499][3] +coeff5*table[499][4] +coeff6*table[499][5]
+coeff7*table[499][6] +coeff8*table[499][7] +coeff9*table[499][8]
+coeff10*table[499][9] +coeff11*table[499][10] +coeff12*table[499][11]
+coeff13*table[499][12] +coeff14*table[499][13] +coeff15*table[499][14]
+coeff16*table[499][15] +coeff17*table[499][16] +coeff18*table[499][17]
+coeff19*table[499][18] +coeff20*table[499][19] +coeff21*table[499][20]
+coeff22*table[499][21] +coeff23*table[499][22] +coeff24*table[499][23]
+coeff25*table[499][24] +coeff26*table[499][25] +coeff27*table[499][26]
+coeff28*table[499][27] +coeff29*table[499][28] +coeff30*table[499][29]
+coeff31*table[499][30] +coeff32*table[499][31] +coeff33*table[499][32]
+coeff34*table[499][33] +coeff35*table[499][34] ;
bruteForceSum =
point1 +
point2 + ... +
point500
;
return bruteForceSum;
}//DoBruteForceCompute
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leppie,
Does CodeDom CodeSnippetStatement take care of breaking long lines or does it too have a limit on the length of a string it can take?
Dave
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You pretty lazy for a mountain biker.... just make a wrapper method
leppie::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.
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...probably more like I've taken too many crashes on my head
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Just out of interest, are you unrolling your loops purely for performance reasons? What is the measured difference in performance between using the loop and unrolling it?
Andy
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Yes, I'm unrolling the loops for performance reasons. So far, in my timing tests, the unrolled loops are about 5-10 times SLOWER (it's not the example code I posted. In that code, the unrolled loops are faster). Figure that one out.
There is a range of performance differences. Unrolling a loop AND hard-coding the logic (via reflection emit) is about 3000% faster according to Jesse Liberty in his Programming C# book. On the other hand, in my complex case where I unroll the loop but still require 2 dimensional array lookups in the unrolled lines of code, I see the slower performance I quoted above (average loop 190ms, average unrolled code 980ms).
When I get a chance, I could post my code (if anyone is interested, that is).
Dave
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Hi,
I am deriving a DataSet using ReadXMLSchema method from a XML Schema Definition file.
I want to fill values in the Tables of the Data Set. There are some Tables that are complex Types. How do I fill values in such columns.
For Ex:
Table A
-----Table B (Attributes: 1,2,3,4)
-----Table C (Attributes: Table D, complexType)
------------Table D (Attributes: 1)
--------------------Table E ((Attributes: 1,2)
B & C are child of A. D & E are child of C.
C only has one column which is a reference to Table D.
How do I fill the values for the column in Table C , which is Table D (complex type)?
Paul
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How can you add "user" to "COM+ security role" programmatically?
You specify security role permitted to access a component with SecurityRole attribute:
[assembly: SecurityRole("SomeComponentUser")] on assembly level, or
[SecurityRole("SomeComponentUser")] on class or method level.
Now, I understand you can add user to a specific security role using COM+ Admin Tool (MMC), but is there a way to do this programmatically?
Thanks!
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Dear, Sir.
My class has two ImageList and two ImageIndex properties.
How to tell propertyGrid know that LargeImageList is for LargeImageIndex and SmallImageList is for SmallImageIndex?
The code below will display SmallImageList item on dropdown of both LargeImageIndex and SmallImageIndex property.
//LargeImage
public ImageList LargeImageList
{
get { return _largeImageList; }
set { _largeImageList = value; }
}
[TypeConverter(typeof(ImageIndexConverter)), Editor("System.Windows.Forms.Design.ImageIndexEditor, System.Design,Version=1.0.3300.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",typeof(System.Drawing.Design.UITypeEditor))]
public int LargeImageIndex
{
get { return _LargeImageIndex; }
set { _LargeImageIndex = value; }
}
//SmallImage
public ImageList SmallImageList
{
get { return _smallImageList; }
set { _smallImageList;} = value; }
}
[TypeConverter(typeof(ImageIndexConverter)), Editor("System.Windows.Forms.Design.ImageIndexEditor, System.Design,Version=1.0.3300.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",typeof(System.Drawing.Design.UITypeEditor))]
public int SmallImageIndex
{
get { return _SmallImageIndex; }
set { _SmallImageIndex = value; }
}
Thank You
Sorry for bad English
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How do i get the text for a listview subitem?
I have two listviews and tview and cview how do i get the subitem from tview i want to get it in another click event?
ListViewItem item2 = new ListViewItem();
item2.Checked = true;
item2.ImageIndex = 0;
tview.Items.Add(item2);
item2.SubItems.Add(CBTaxiId.SelectedItem.ToString());
Da Intern
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jphuphilly wrote:
How do i get the text for a listview subitem?
tview.Items[x].SubItems[1].Text
listViewItem.SubItems[0].Text returns the text of the item,
listViewItem.SubItems[1] returns the first subitem, .Subitems[2] the second subitem, and so on.
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Hi, there
Please help me with this. I try to show some message in a TextBox. Because it could be used by more than one threads, I lock ( this ) before I show the message. But it turns out, the 2nd thread can never get through "lock (this)". Could anyone please tell me why.
Thanks in advance.
public class LogClass <br />
{<br />
private TextBoxBase outputWin = null;<br />
public TextBoxBase OutputWindow <br />
{<br />
get <br />
{<br />
return outputWin;<br />
} <br />
}<br />
<br />
public LogClass(TextBoxBase win)<br />
{<br />
outputWin = win;<br />
}<br />
<br />
public void ShowMessage(string message)<br />
{<br />
string s = System.DateTime.Now.ToString() + ": " + message + "\r\n";<br />
lock ( this ) <br />
{<br />
if ( outputWin != null ) <br />
{<br />
if ( s.Length + outputWin.TextLength > outputWin.MaxLength ) <br />
{<br />
outputWin.Text = "";<br />
}<br />
outputWin.Text += s;<br />
}<br />
} }<br />
}<br />
}
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In the object browser, the comments of a class or its member's summary and parameters can be displayed at the bottom of the window (these comments use "///"). When I compile the project to a .dll, reference this .dll into another solution, the comments of the classes in this .dll can't displayed in object browser. Why? How can I fix it?
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You need to:
1) Turn on XML comments in the library project
2) Name the file the same thing as the dll (ie utility.xml for utility.dll)
If you do that, the IDE will find the comments.
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