topic System.AccessViolationException while trying to get layername in .NET Forum

System.AccessViolationException while trying to get layername

r00teniy — Thu, 20 Oct 2022 08:57:01 GMT

Hello, I am getting "System.AccessViolationException: Attempted to read or write protected memory." while trying go get layer of blockref in array.

Here is part of the code that give exeption, it always gives it then i try to get (obj as BlockReference).Layer, if i remove it, it works fine:

if (AssocArray.IsAssociativeArray(objectId)) { using (BlockReference br = objectId.Open(OpenMode.ForRead) as BlockReference) { using (DBObjectCollection brs = new DBObjectCollection()) { br.Explode(brs); if (brs != null && brs.Count > 0) { foreach (DBObject obj in brs) { for (int j = 0; j < laylistBL.Length; j++) { if (obj is BlockReference && (obj as BlockReference).Layer == laylistBL[j]) { TableValues[12 + j] += 1; } obj.Dispose(); } } } } } }

I found similar code and modified it for myself here.

Can you please point out what I'm doing wrong?

Re: System.AccessViolationException while trying to get layername

_gile — Thu, 20 Oct 2022 10:22:31 GMT

hi,

What if you iterate through the BlockTableRecord entities of the BlockReference instead of exploding it?

Something like this (not tested).

if (AssocArray.IsAssociativeArray(objectId)) { using (BlockReference br = (BlockReference)objectId.Open(OpenMode.ForRead)) { using (BlockTableRecord btr = (BlockTableRecord)br.BlockTableRecord.Open(OpenMode.ForRead)) { foreach (objectId id in btr) { if (id.ObjectClass.Name = "AcDbBlockReference") { using(BlockReference bRef = (BlockReference)id.Open(OpenMode.ForRead)) { for (int j = 0; j < laylistBL.Length; j++) { if (bRef.Layer == laylistBL[j]) { TableValues[12 + j] += 1; } } } } } } } }

Re: System.AccessViolationException while trying to get layername

r00teniy — Thu, 20 Oct 2022 10:26:06 GMT

Thank you, will try to work in this direction.

Re: System.AccessViolationException while trying to get layername

_gile — Thu, 20 Oct 2022 10:25:27 GMT

Oops!...

I forgot casting the BlockTableRecord.

I corrected the upper code replacing:

using (BlockTableRecord btr = br.BlockTableRecord.Open(OpenMode.ForRead))

with:

using (BlockTableRecord btr = (BlockTableRecord)br.BlockTableRecord.Open(OpenMode.ForRead))

Re: System.AccessViolationException while trying to get layername

r00teniy — Thu, 20 Oct 2022 10:42:50 GMT

For me this line did it, thank you:
using (BlockTableRecord btr = br.DynamicBlockTableRecord.Open(OpenMode.ForRead) as BlockTableRecord)