Re: AccessViolationException in OdbcDataReader - C# Discussion Boards

it did not help

It has to, because that fixes your ( very obvious ) bug. How about you learn to use the debugger, then examine the code to work out exactly what is wrong ? You can then ask here and you'll get a real answer, because you will ask an intelligent question

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

In the first message, I pointed to a code string with an error

Yes that is true, you get expection when accsess an index that doesn't exsist.

If you have 3 indexes.

for (int i=0; i<=index+1;i++)

first part: i<=index. when you count 3, loop will do extra loop because of '<=' will do extra loop till i gets to 3. but it is zero based index and if i gets to 3, there are 4 indexes already, while reader have only 3. The second part is +1. Lose it. if you wan't to keep <= then use instead index+1 use index-1

edit: Also all exceptions comes with description, probably yours came with "Index out of boundary". When you wan't to know what is wrong,sometimes it is not enough the place and witch expection. All exceptions comes with a message

Frozzeg wrote:
In the first message, I pointed to a code string with an error

You only pointed where AccessViolationException happens

edit 2: Copy paste from MSDN

Remarks
An access violation occurs in unmanaged or unsafe code when the code attempts to read or write to memory that has not been allocated, or to which it does not have access. This usually occurs because a pointer has a bad value. Not all reads or writes through bad pointers lead to access violations, so an access violation usually indicates that several reads or writes have occurred through bad pointers, and that memory might be corrupted. Thus, access violations almost always indicate serious programming errors. In the .NET Framework version 2.0, an AccessViolationException clearly identifies these serious errors.

In programs consisting entirely of verifiable managed code, all references are either valid or null, and access violations are impossible. An AccessViolationException occurs only when verifiable managed code interacts with unmanaged code or with unsafe managed code.

Version Information
This exception is new in the .NET Framework version 2.0. In earlier versions of the .NET Framework, an access violation in unmanaged code or unsafe managed code is represented by a NullReferenceException in managed code. A NullReferenceException is also thrown when a null reference is dereferenced in verifiable managed code, an occurrence that does not involve data corruption, and there is no way to distinguish between the two situations in versions 1.0 or 1.1.

modified on Monday, August 17, 2009 5:09 AM

Frozzeg wrote:
for (int i = 0; i <= integer+1; i++)

How very odd. Why would you want to count to integer+1, that will be 2 more than the number of fields.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

It was a stupid mistake in "for", I mistakenly used instead of - +, thx but i still have AccessViolationException

P.S. sry for my English

And what kind of accsess vaiolation occorus: please post detail. Including its message

System.AccessViolationException was unhandled
Message="Attempting to read or write protected memory. This often indicates that other memory is damaged."
Source="System.Data"
StackTrace:
в System.Data.Common.UnsafeNativeMethods.SQLGetData(OdbcStatementHandle StatementHandle, UInt16 ColumnNumber, SQL_C TargetType, CNativeBuffer TargetValue, IntPtr BufferLength, IntPtr& StrLen_or_Ind)
в System.Data.Odbc.OdbcStatementHandle.GetData(Int32 index, SQL_C sqlctype, CNativeBuffer buffer, Int32 cb, IntPtr& cbActual)
в System.Data.Odbc.OdbcDataReader.GetData(Int32 i, SQL_C sqlctype, Int32 cb, Int32& cbActualOut)
в System.Data.Odbc.OdbcDataReader.internalGetString(Int32 i)
в System.Data.Odbc.OdbcDataReader.GetValue(Int32 i, TypeMap typemap)
в System.Data.Odbc.OdbcDataReader.GetValue(Int32 i)
в FMySQLClient.MySQL.FetchArray(OdbcDataReader& reader) в C:\FMySQLClient\FMySQLClient\MySQL.cs:line 199
в FMySQLClient.Form1.button1_Click(Object sender, EventArgs e) в C:\FMySQLClient\FMySQLClient\Form1.cs:line 30
в System.Windows.Forms.Control.OnClick(EventArgs e)
в System.Windows.Forms.Button.OnClick(EventArgs e)
в System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
в System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
в System.Windows.Forms.Control.WndProc(Message& m)
в System.Windows.Forms.ButtonBase.WndProc(Message& m)
в System.Windows.Forms.Button.WndProc(Message& m)
в System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
в System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
в System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
в System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
в System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
в System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
в System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
в System.Windows.Forms.Application.Run(Form mainForm)
в FMySQLClient.Program.Main() в C:\FMySQLClient\FMySQLClient\Program.cs:line 18
в System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
в System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
в Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
в System.Threading.ThreadHelper.ThreadStart_Context(Object state)
в System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
в System.Threading.ThreadHelper.ThreadStart()
InnerException:

Does the loop run at least once?

I suspect it is connector problem. You coud try using MySql Connector/Net(I Used it, because other connectors were painfull to get them working). It is a form of external dll that you can reference to it. And you are not required to install it as it is required with ODBC connector.

Try asking in their forum, you coud stumble upon a bug.

"Does the loop run at least once?" - no

Ok, thx

I say that you are to use.

for (int i = 0; i <= integer-1; i++)
or
for (int i = 0; i < integer; i++)

If reader.FieldCount = 4 get the i parts 0,1,2,3

hi friend's
i design an application that when start need to read a serial number from a server that this serial number saved in a sql database. but i dont know how to set my connection string and so on...
please give me a asolution
thank you

nobody help you...
you have to help you yourself
and this is success way.

this site will help you...
http://www.connectionstrings.com/[^]

Padmanabhan
My Articles:
Articles[^]
My latest Article:
Word Automation[^]

thank you
this site is suitable and useful.

nobody help you...
you have to help you yourself
and this is success way.

Beginners guide to accessing SQL Server through C#[^]

Hi,
I am using c#.net and Microsoft.Office.Interop.Word dll to read the ms word document content. My requirement is to read all available bookmarks from the document.
I am able to read the number of bookmarks(count only) but failed to read the bookmark names.
Here is the code for reading bookmark count.

_Application wdApp = new Microsoft.Office.Interop.Word.Application();
_Document Doc = new Microsoft.Office.Interop.Word.Document();
Microsoft.Office.Interop.Word.Range wdRange;
object optional = System.Reflection.Missing.Value;
Doc = wdApp.Documents.Open(ref _fileName, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional);
int intParaCount;
intParaCount = Doc.Bookmarks.Count;

Please provide the code for reading the available bookmark names from the word document.
Thanks in advance.

Veerendra

try
doc.Bookmarks.get_Item(index).name;

Padmanabhan
My Articles:
Articles[^]
My latest Article:
Word Automation[^]

Hi,
I am using .NET to query indexing server (search engine for our Intranet)
If the user searches for "the,he,she,in" or "a" etc they will get an error page stating - "(The query contained only ignored words.)"
What is the best way to catch this and deliver something meaningful back to the page.

It looks as you have problems with SQL Server Full-Text Search.
If I'm right you should post your question into General Database forum.

Life is a stage and we are all actors!

Hi
I am new in asp.net can some help me how to start an online chat application in asp.net using c#..MY mail id is guptagaurav212@gmail.com

Thanks in advance
Gaurav Gupta

GauravGupta212 wrote:
Hi

I am new in asp.net can some help me how to start an online chat application in asp.net using c#..MY mail id is guptagaurav212@gmail.com

Thanks in advance
Gaurav Gupta

Wow. Let me spell it out for you.

1 - posting your email, which will get you spam from people who have nothing to do with this site, and almost certainly nothing else
2 - this is NOT the ASP.NET forum
3 - we are NOT here to tell you how to use google.
4 - it is INCREDIBLY rude to delete your message, no matter how stupid. It just clutters the forums.

The only way to write a chat app is with AJAX. ASP.NET has next to nothing to do with it. I suggest buying an AJAX book and reading it before coming back and using the correct forum to ask specific questions.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

[Message Deleted]

You've done just about everything wrong here. Try reading the guide on how to ask questions, do some research, and try using the right forum when you have a question that is more specific than 'do my work for me'.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Dear All, I am trying to prepare my self for a project which is Distributed and also disconnected at most points.
i would appreciate any reference,website or books of distributed application development which i can do it through c#.

Abdul Rahaman Hamidy
Database Developer
Kabul, Afghanistan

This is a really nice beginners book for distributed systems. Smile | :)

Life is a stage and we are all actors!