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Hi C# gurus,
I have a casting problem in the following set of classes:
<br />
class Polymino<br />
{<br />
...<br />
}<br />
<br />
class Tetramino : Polymino<br />
{<br />
...<br />
}<br />
<br />
class ITetramino : Tetramino<br />
{<br />
...<br />
}<br />
<br />
class GameBoard<br />
{<br />
...<br />
private Polymino m_polymino;<br />
...<br />
<br />
public Polymino polymino<br />
{<br />
get { return m_polymino; }<br />
set { m_polymino=value; }<br />
}<br />
...<br />
}<br />
<br />
class Tetrion : UserControl<br />
{<br />
...<br />
private GameBoard m_gameBoard;<br />
...<br />
private Tetramino m_currentTetramino;<br />
...<br />
<br />
public void Start()<br />
{<br />
m_currentTetramino=GetRandomTetramino();<br />
m_gameBoard.polymino=m_currentTetramino;<br />
}<br />
...<br />
<br />
private Tetramino GetRandomTetramino() ...<br />
}<br />
Polymino is the base class of all.
In the Tetrion.Start method, when I call m_gameBoard.polymino=m_currentTetramino, I have an error in the m_gameBoard.polymino property call. I guess it's a casting problem. In C++ this kind of thinking is okay, but it seems that it does not work in C#, even if I do a cast like that: m_gameBoard.polymino=(Polymino) m_currentTetramino.
Can anybody help me and tell me why the debugger stops at this call?
Best regards.
Thanks.
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What is the exact exception you are receiving, including the Type and message (if any)?
Microsoft MVP, Visual C#
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Hi Heath,
I have no exception... The call stack is full of "Tetour.exe!Tetour.GameBoard.set_polymino(Tetour.Polymino value = {Tetour.STetramino}) Line 49 + 0xa bytes"
STetramino is derived from Tetramino which is derived from Polymino. as STetramino is a specialized class based on Polymino class, the casting should work... like for C++... 
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Yes it should, just like the ArrayList which collects objects can take an instance of any class no matter far down the derivation tree it is.
Are these simple classes or controls (or possibly modify control properties directly)? If so, are you using multiple threads? Odd problems can occur when getting and most often setting properties on controls from another thread besides the main UI thread.
What causes the break into the debugger if you're not seeing an exception? Are you just stepping through lines or does it break while executing?
Microsoft MVP, Visual C#
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it breaks while executing.
All the classes I show you are simple classes. the only classes derived from a UserControl are the Tetrion and TetraminoPreview classes.
The complete code of Tetrion.Start() method looks like this:
<br />
public void Start()<br />
{<br />
Debug.WriteLine("Tetrion.Start");<br />
m_gameStatus=GameStatus.gameStarted;<br />
m_gameBoard.Initialize();<br />
<br />
m_currentTetramino=GetRandomTetramino();<br />
m_gameBoard.polymino=m_currentTetramino;<br />
m_nextTetramino=GetRandomTetramino();<br />
<br />
if (m_tetraminoView != null)<br />
{<br />
m_tetraminoView.tetramino=m_nextTetramino;<br />
m_tetraminoView.Display=m_bShowNextTetramino;<br />
m_tetraminoView.Draw3D=m_gameBoard.Draw3D;<br />
m_tetraminoView.DrawGrid=m_gameBoard.DrawGrid;<br />
}<br />
<br />
Invalidate();<br />
}<br />
<br />
The code stops its execution at the call m_gameBoard.polymino=m_currentTetramino;
while there are no break points.
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you were right. the exception is:
"An unhandled exception of type 'System.StackOverflowException' occurred in Tetour.exe"
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I suspect the exception is actually being thrown because of GetRandomTetramino(). In some cases, the break appears on the next line after the offending line because the exact problem is not addressable. A StackOverflowException would most likely be one of those exception cases. What does the implementation for GetRandomTetramino() look like?
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The GetRandomTetramino method selects a specialized tetramino. The code looks like this:
<br />
private Tetramino GetRandomTetramino()<br />
{<br />
Random rnd=new Random(DateTime.Now.Millisecond);<br />
Tetramino tetramino=null;<br />
<br />
TetraminoType[] tetraminoType=(TetraminoType[]) Enum.GetValues(typeof(TetraminoType));<br />
<br />
switch (tetraminoType[rnd.Next(tetraminoType.Length)])<br />
{<br />
case TetraminoType.iTetramino:<br />
tetramino=new ITetramino();<br />
break;<br />
<br />
case TetraminoType.jTetramino:<br />
tetramino=new JTetramino();<br />
break;<br />
<br />
case TetraminoType.lTetramino:<br />
tetramino=new LTetramino();<br />
break;<br />
<br />
case TetraminoType.oTetramino:<br />
tetramino=new OTetramino();<br />
break;<br />
<br />
case TetraminoType.sTetramino:<br />
tetramino=new STetramino();<br />
break;<br />
<br />
case TetraminoType.tTetramino:<br />
tetramino=new TTetramino();<br />
break;<br />
<br />
case TetraminoType.zTetramino:<br />
tetramino=new ZTetramino();<br />
break;<br />
<br />
default:<br />
tetramino=new ITetramino();<br />
break;<br />
}<br />
<br />
return tetramino;<br />
}<br />
<br />
the shapes are correctly coded because when I do a m_tetraminoPreview.tetramino=new ITetramino for example, it shows me the correct shape.
There is no spoon.
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It's not a problem with casting, but with too many method calls on the stack (hence the StackOverflowException). Somewhere, you either have an unterminated recursive loop or are too deep in method calls. Examine the stack trace, which should give you some insight into how many calls are on the stack and which one is the offending call.
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That's what I wanted to do, but the call stack is full of the same message:
"Tetour.exe!Tetour.GameBoard.set_polymino(Tetour.Polymino value = {Tetour.OTetramino}) Line 49 + 0xa bytes C#"
when I insert a breakpoint in the GameBoard.polymino set property, it always loop in this property, while I do only 1 call. I think it does not have to loop inside this call because I call this property only one time, and it's just an assignement.
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I guess you did say "full of" in a previous thread. Sorry I missed it.
This is an odd problem indeed. Is the original code you posted for the polymino property (which, using the .NET naming guidelines, should actually be Polymino, but I won't get started on that since it's a different topic) correctly declare the same as it is in your code (i.e., is what you posted the exact same thing as what's in your code)?
That's obviously the offending line. Are you sure you're not typing polymino again instead of m_polymino? This would definitely cause the recursion that's causing the stack overflow.
Microsoft MVP, Visual C#
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I have found the problem it's in the GameBoard.polymino property.
I wrote:
<br />
public Polymino polymino<br />
{<br />
get { return m_polymino; }<br />
set { polymino=value; }
}<br />
while it was:
<br />
public Polymino polymino<br />
{<br />
get { return m_polymino; }<br />
set { m_polymino=value; }
}<br />
I forgot the "m_" so it made a recursive call to itself and then the stack overflowed.  When you talk about "recursive" I checked the code of the property I wrote, and all came from this bad line. And now, the casting works the way I expected: like in C++. I correctly wrote the property in the topic, but not in the project  
I hope the engine of this game will be finished soon :p
Thanks for the help Heath!
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after binding my table to the datagrid what is an easy way to make a column readonly please
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Set DataGrid.ReadOnly to true. It's important to look at the class documentation, at least for simple things like this.
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that will do the whole grid i only want a column?
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Then explicitly define a DataGridTableStyle with DataGridColumnStyle derivatives matching up with your columns you want to display. For any columns you want to disable editing, set DataGridColumnStyle.ReadOnly to true. For more about tables styles, see the documentation for the DataGridTableStyle[^] class in the .NET Framework SDK. It also includes sample code.
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will this work after binding my grid to the table that i am create from the database ie DataTable tbl = LoadData();
MyDatagrid.DataSource = tbl;
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Yes, and you don't need to re-initialize it. You can even add multiple table styles to handle multiple data sources. Again, read the documentation I provided a link for.
Microsoft MVP, Visual C#
My Articles
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on the case let you know how i get on many thanks
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I cant see where i am going wrong as my loop shows the readonly to be false for every column even though i am setting them to true in my routine and when i loop through the columnsstyle collection i get false for every one???
private void LoadInvoice(DataGrid invoiceJob,ComboBox phaseName)
{
job = new Job();
DataTable list = job.LoadPhasePayers(Convert.ToInt32(phaseName.SelectedValue.ToString()));
invoiceJob.DataSource = list;
AddCustomDatagridStyle(invoiceJob);
foreach(DataGridTableStyle ts in dtgCInvoice.TableStyles)
{
Debug.WriteLine(ts.ReadOnly);
}
}
private void AddCustomDatagridStyle(DataGrid myGrid)
{
DataGridTableStyle ts1 = new DataGridTableStyle();
ts1.MappingName = "PhasePayers";
DataGridColumnStyle textCol = new DataGridTextBoxColumn();
textCol.MappingName = "Payer";
textCol.HeaderText = "Payer";
textCol.Width = 250;
textCol.ReadOnly = true;
ts1.GridColumnStyles.Add(textCol);
myGrid.ReadOnly = true;
myGrid.TableStyles.Add(ts1);
DataGridColumnStyle textCol2 = new DataGridTextBoxColumn();
textCol.MappingName = "Net";
textCol.HeaderText = "Net";
textCol.Width = 250;
textCol.ReadOnly = true;
ts1.GridColumnStyles.Add(textCol2);
myGrid.TableStyles.Add(ts1);
DataGridColumnStyle textCol3 = new DataGridTextBoxColumn();
textCol.MappingName = "VAT";
textCol.HeaderText = "VAT";
textCol.Width = 250;
textCol.ReadOnly = true;
ts1.GridColumnStyles.Add(textCol3);
myGrid.TableStyles.Add(ts1);
DataGridColumnStyle textCol4 = new DataGridTextBoxColumn();
textCol.MappingName = "Gross";
textCol.HeaderText = "Gross";
textCol.Width = 250;
textCol.ReadOnly = true;
ts1.GridColumnStyles.Add(textCol4);
myGrid.TableStyles.Add(ts1);
}
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As I said before, do not initialize the table and column styles every time you set your DataSource, which you currently are. You only need to do this once. The way you're currently doing it, you add new column and table styles each time you set the data source, leading to increasing memory consumption, performance degradation, and other unforseen problems with having the same table style added multiple times. Also, how is setting every column's ReadOnly property to true different from simply setting DataGrid.ReadOnly to true?
The actual problem is most likely because you're DataGridTableStyle.MappingName is set to the table name of the DataSource you're using, which is a DataTable. If you were to actually use a DataSet and set that as the DataSource with the table name set in the DataGrid.DataMember property (which should be the same as the table style you want to use, since you can have more than one table style). If you set the DataGrid.DataSource to a DataTable,. then IIRC the DataGridTableStyle.MappingName should be an empty string or null (either would work - just don't set it to begin with, though).
Microsoft MVP, Visual C#
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many thanks for persevering with me i got it thanks to you, setting the mapping name to null was the big key and i am glad you spotted my method of setting on every load i was getting tired and difflated at that stage. I am using tables rather than the overhead of a dataset being returned everytime, i have got styles to work with dataset but my little brain was struggling to get it to work with a table now i am off and running again looking for my next brickwall to knock down  ))))))
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now it is getting bigger when i switch between design view and code view it is very slow any ideas on how to spped it up
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are you placing any background image to your window?
I usually disable it.
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