Method RVAs: offset or VA?

dotnet framework


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Method RVAs: offset or VA?

Postby TWFyYyBFYWRkeQ » Tue, 28 Sep 2004 02:31:01 GMT


I'm writing an application that uses the Profiler API and the unmanaged 
metadata API to obtain metadata for modules from the 
ICorProfilerCallback::ModuleLoadFinished() event as well as for executables 
that I map into memory myself.  In both cases I'm able to obtain the 
IModuleInfo iface and enumerate the methods.  

I've noticed that the method RVA returned by GetMethodProps() is sometimes a 
real RVA and sometimes an offset.  This causes havok because I'm trying to 
access the method's bytecode in memory.  If its an RVA I have to call 
ImageRvaToVa(), otherwise I just have to add it to the base load address.

It seems to be treated as an offset if the CLR has loaded the module and as 
a RVA if the file was manually mapped into memory.  Is this true?  Strangely, 
Rotor always treats it as an RVA.  If you look at CorMap::ReadHeaders() in 
cormap.cpp in Rotor you'll see a magic flag called bDataMap that proves that 
RVAs have a dual nature.

Right now I have a kludge that calls ImageRvaToVa() and examines the first 
byte of the returned ptr.  If its not TinyFormat or FatFormat then I treat 
the RVA as an offset.  Is there a way, given a module's base load address, or 
perhaps a flag in the MethodProps, to determine if its RVAs are really RVAs 
or if they are offsets?



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1.Error "Cast from type 'DataRowView' to type 'String' is not va


Thank you very much. Using the DataRelation worked. I just had to specify 
the "RelationName" attribute of my DataRelation:

DataGrid1.DataSource = MyDataSet.Tables(0)
DataGrid1.DataMember = MyDataRelation.RelationName


"Bart Mermuys" wrote:

> Hi,
> "Richard Mueller" < XXXX@XXXXX.COM > wrote in 
> message news: XXXX@XXXXX.COM ...
> > I've seen this problem posted several times, but have not yet seen a
> > solution.  I make a connection to a SQL database and use a DataAdapter 
> > object
> > to fill a DataSet object with several tables. A DataRelation object links 
> > the
> > tables by an ID column. I bind the parent table to a combo box and a child
> > table to a DataGrid control using a DataView object. I want the DataGrid
> > control to reflect the selection in the combo box. For the combo box,
> > DisplayMember is a text string while ValueMember is the ID field 
> > (integer).
> > In brief:
> >
> > Private Sub Form1_Load(....)
> >    ' Connect to database, populate Tables in DataSet,
> >    ' setup DataViews, and define DataRelations.
> >    Call Populate()
> >
> >    ComboBox1.DataSource = MyDataSet.Tables(0)
> >    ComboBox1.DisplayMember = MyDataSet.Tables(0).Columns(1).ColumnName
> >    ComboBox1.ValueMember = MyDataSet.Tables(0).Columns(0).ColumnName
> >    Me.BindingContext(MyDataSet.Tables(0)).Position = 0
> >
> >    Dim strFilter As String
> >    strFilter = "ID = " & ComboBox1.SelectedValue
> >    MyDataView.RowFilter = strFilter
> >    DataGrid1.DataSource = MyDataView
> > End Sub
> >
> > Private Sub ComboBox1_SelectedValueChanged(....)
> >    Dim strFilter As String
> >    If (ComboBox1.SelectedIndex <> -1) Then
> >        strFilter = "ID = " & ComboBox1.SelectedValue
> >        MyDataView.RowFilter = strFilter
> >    End If
> > End Sub
> >
> > Strangely, the code works if I comment out the
> > ComboBox1_SelectedValueChanged sub. I can hard code in Form1_Load to 
> > select
> > the first (index=0), or any other item in the combo box, and the DataGrid
> > reflects the correct item. But of course I cannot select another item in 
> > the
> > combo box and have the DataGrid reflect this. The error is raised in
> > CombBox1_SelectedValueChanged on the statement:
> >
> > strFilter = "ID = " & ComboBox1.SelectedValue
> >
> > and the error is "Cast from type 'DataRowView' to type 'String' is not
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> > that I assign a DataSource to the combo box, plus the DisplayMember and
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> > when
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> You're probely getting this error because SelectedValueChanged fires after 
> setting the ComboBox.DataSource but before you have set the 
> ComboBox.ValueMember.  So at that point SelectedValue returns a DataRowView. 
> So you could change it to:
> Private Sub ComboBox1_SelectedValueChanged(....)
>   Dim strFilter As String
>   If (ComboBox1.SelectedIndex <> -1) AndAlso _
>       (ComboBox1.ValueMember<>"") Then
>        strFilter = "ID = " & ComboBox1.SelectedValue
>         MyDataView.RowFilter = strFilter
>    End If
> End Sub
> BUT, if you have a DataRelation between the two DataTables, then you don't 
> need to do that, you can let the child rows be _automatically_ filtered. 
> All you have to do is bind the DataGrid to the same DataSource as the 
> ComboBox and set DataGrid.DataMember to the name of the DataRelation between 
> them:
> Private Sub Form1_Load(....)
>   ' Connect to database, populate Tables in DataSet,
>   ' setup DataViews, and define DataRelations.
>   Call Populate()
>    ComboBox1.DataSource = MyDataSet.Tables(0)
>    ComboBox1.DisplayMember = MyDataSet.Tables(0).Columns(1).ColumnName
>    ComboBox1.ValueMember = MyDataSet.Tables(0).Columns(0).ColumnName
>    DataGrid1.DataSource = MyDataSet.Tables(0)
>    DataGrid1.DataMember = "NameOfRelationBetweenTables"
> End Sub
> This way the DataGrid should be auto filtered when you change ComboBox 
> selection.
> HTH,
> Greetings
> > Note. My code is based on "Using a Data Set with Tables in a Parent-Child
> > Relationship" from Chapter 10 (pg. 402-408) of "Programming Microsoft SQL
> > Server 2000 with Microsoft Visual Basic .NET" by Rick Dobson.
> >
> > Richard

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I am encountering the following problem with a call to a stored procedure 
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The stored procedure looks like this:

@id1 int,
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Set @flag1 = (SELECT flag From MyTable
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The C# code:
sqlCmdData.CommandText = "sproc";
sqlCmdData.Parameters.AddWithValue("@id1", _id1);
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int _status = Convert.ToInt32(sqlParmResult.Value);  // This works OK
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This throws a NULL exception.

Any ideas on what may be happening here?

I would appreciate any help.


3.OracleCommadbuilder: Exception: Parameter 'p1': No size set for va


I am re-raising this post as we have a developer here running into the same issue. Is this a bug or a feature? Are there any similar bugs or features of other datatypes that we should be aware of?


"Peter Meinl" wrote:

> When updating an Oracle Varchar2 column with an empty string "" using the
> OracleCommandBuilder generated UpdateCommand the follwing error is thrown:
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> above error.

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