Logix ReadUDT exception

[Tped]

I have my udt class created, and a tag defined to it (TestData as UDT_Results).  When i run this line
TestData = EthernetIPforCLXCom1.ReadUDT(Of UDT_Results)("TestResults", 1)
i get this back

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=MfgControl.AdvancedHMI.Drivers
  StackTrace:
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.a[a]()
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.GetObjectFromBytes[t](Byte[] data, Int32 startIndex)
   at MfgControl.AdvancedHMI.Drivers.EthernetIPforCLX.ReadUDT[t](String startAddress, Int32 numberOfElements)
   at MfgControl.AdvancedHMI.FormMain.Subscription_DataReceived(Object sender, PlcComEventArgs e) in D:\Documents\Advanced HMI\3120 Pentair Data Management\AdvancedHMI\FormMain.vb:line 61
   at AdvancedHMIDrivers.EthernetIPforCLXCom.DataRecSync(Object e) in D:\Documents\Advanced HMI\3120 Pentair Data Management\AdvancedHMIDrivers\AllenBradley\EthernetIPforCLXCom.vb:line 291


Not sure what i'm doing wrong, I'm a PLC guy, this vb stuff is pretty new to me.

[Archie]

There is an issue with ReadUDT in 3.99y Beta 31, this is going to be fixed in Beta 32

[Archie]

Beta 32 is now available. Try this version to see if it works for ReadUDT:

https://www.advancedhmi.com/forum/index.php?topic=2058.180

[gti13]

I'm also experiencing this null reference exception. Upgrading to Beta 32 does not appear to have resolved the issue, at least not for my scenario.

Code: [Select]

//readData = ethernetIPforCLXCom1.ReadUDT<CompleteUDT>("TestData");
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.a[a]()
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.GetObjectFromBytes[t](Byte[] data, Int32 startIndex)
   at MfgControl.AdvancedHMI.Drivers.EthernetIPforCLX.ReadUDT[t](String startAddress, Int32 numberOfElements)
   at MfgControl.AdvancedHMI.Drivers.EthernetIPforCLX.ReadUDT[t](String startAddress)
   at MainForm.PLC_Read(String element) in C:\Project\MainForm.cs:line 363

//readData = ethernetIPforCLXCom1.ReadUDT<CompleteUDT>("TestData", 1)[0];
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.a[a]()
   at MfgControl.AdvancedHMI.Drivers.UDTBytesToClass.GetObjectFromBytes[t](Byte[] data, Int32 startIndex)
   at MfgControl.AdvancedHMI.Drivers.EthernetIPforCLX.ReadUDT[t](String startAddress, Int32 numberOfElements)
   at MainForm.PLC_Read(String element) in C:\Project\MainForm.cs:line 363
I have a feeling this may be caused by having a nested UDT, similar to the following:

Code: [Select]

public class CompleteUDT
{
public PartUDT PartOne;
public PartUDT PartTwo;
public PartUDT PartThree;
public CompleteUDT()
{
PartOne = new PartUDT();
PartTwo = new PartUDT();
PartThree = new PartUDT();
}       

public class PartUDT
{
public string DetailOne;
public short DetailTwo;
public float DetailThree;
public short[] DetailFour;
public float[] DetailFive;
public PartUDT()
{
DetailOne = string.Empty;
DetailTwo = 0;
DetailThree = 0f;
DetailFour = new short[64];
DetailFive = new float[64];
}
}
}
WriteUDT works fine, but ReadUDT on the root UDT returns the null reference exception.

Code: [Select]

CompleteUDT completeData = new CompleteUDT();

// Assign values
PartUDT partData = new PartUDT();
dynamic value = "0";
// Repeat following for DetailOne, DetailTwo, and DetailThree
value = "some string";
partData.DetailOne = Convert.ChangeType(value, partData.DetailOne.GetTypeCode());
// Repeat following for DetailFive (Array types)
for (int i = 0; i < partData.DetailFour.Length; i++) {
value = i;
partData.DetailFour = Convert.ChangeType(value, partData.DetailFour[i].GetTypeCode());
}
completeData.PartOne = partData;
// Repeat the block above for PartTwo and PartThree

// Write CompleteUDT to tag "TestData"
ethernetIPforCLXCom1.WriteUDT("TestData", completeData);

// Read CompleteUDT from tag "TestData"
CompleteUDT readData = new CompleteUDT();
// Cause null reference exceptions:
//readData = ethernetIPforCLXCom1.ReadUDT<CompleteUDT>("TestData");
//readData = ethernetIPforCLXCom1.ReadUDT<CompleteUDT>("TestData", 1)[0];
// Current workaround:
readData.PartOne = ethernetIPforCLXCom1.ReadUDT<CompleteUDT.PartUDT>("TestData.PartOne");
readData.PartTwo = ethernetIPforCLXCom1.ReadUDT<CompleteUDT.PartUDT>("TestData.PartTwo");
readData.PartThree = ethernetIPforCLXCom1.ReadUDT<CompleteUDT.PartUDT>("TestData.PartThree");

[Archie]

There was an issue that would let it work in the development solution, but not in the release package.

Attached is a patched file that should work.

- Download the attached file
- In Solution Explorer, expand down the AdvancedHMIDrivers project
- Right click the Support folder and select Add->Existing Item
- Browse to the location the attached file was downloaded to
- Change the file types to All Files
- Select the MfgControl.AdvancedHMI.Drivers.DLL file
- Make sure it asks to replace the file, if not you missed a step some where
- Rebuild the Solution

[gti13]

Awesome! That appears to have resolved the ReadUDT issue, thank you Archie.