Monday, 29 April 2013

Understanding error codes

Error messages frequently include error codes; sometimes they also include useful text that describes the code, but sometimes they don’t, leaving you to discover what the code means. Here's how I decipher CRM and Windows error codes.

CRM Error Codes
The CRM error codes are (reasonably) well documented here in the CRM SDK. If you’re searching for the code, one thing to watch for is that the code may be referenced with a prefix of 0x (which indicates the code is represented in hex) – e.g. 0x80040201. If you search for the code, it’s best to remove the 0x prefix.

It is also possible that you may receive the code as an integer (e.g. -2147220991). If you do, convert if to hex (I use the Calculator application), then search for it.
Windows Error Codes
There is more variation in how you may identify a Windows error code, but they are ultimately numerical values starting from 1, and (as far as I’m aware) are consistent across versions of Windows. Newer versions of Windows may include error codes that don’t exist in previous versions, but the same error code should have the same meaning across versions.

There is a quick and easy way to get the message associated with a given code – go to a command prompt and enter NET HELPMSG - e.g.

And you’ll get the result
“Access is denied”

This is the message for error code 5 (which is probably the most common code I encounter, though I don’t keep stats on this…)
So, that’s fine if you’ve been given the error code as an integer value (I don’t know what the highest valued error code is – it’s probably either in the high thousands, or maybe 5 digits), but it’s not always that easy.

The code may be in hex(aka hexadecimal). If it contains one of the characters a-f, then it’s in Hex and you’ll need to convert it to decimal. I use the Calculator application to do this. Also, the value may be provided in hex but comes out just as digits. So, if I have an error code, and the message seems entirely irrelevant, I normally convert the code as if it were in hex to decimal, then pass it to NET HELPMSG.
The code may be in hex, but supplied as a 32-bit (or maybe 64-bit) integer with some higher bit flags set, for example:
The prefixes 0x and &H are some ways to indicate the value is in hex, and these prefixes can be discarded. You can also discard all but the last 4 characters (in these examples 0005, 0002 and 0035) and convert them from hex to decimal (in these examples giving 5, 2 and 53 respectively).

Finally, you may get a 32-bit integer with some higher bit flags set, receive the value in decimal, rather than hex. These almost always have the highest bit of a 32-bit value set, which means that in decimal they come out around 2 147 000 000 (or more commonly as a negative number, as they are typically signed integers). So, if I got an error code of -2147024891, I would:
  1. Convert it to hex, giving 80070005
  2. Discard all but the last 4 characters, giving 0005
  3. Convert it back to decimal, giving 5
  4. Run NET HELPMSG 5, and find that I’ve got another ‘Access is denied’ message

Friday, 26 April 2013

The given key was not present in the dictionary - what it means, and how to avoid it

A common error posted on the CRM Development forum is ‘the given key was not present in the dictionary’. This is a relatively easy error to diagnose and fix, provided you know what it means. It will also help to identify the line in the code at which the error occurs, which is most easily determined by debugging.

The error refers to a ‘dictionary’, and a ‘key’. The ‘dictionary’ is a type of collection object (i.e. it can contain many values), and the ‘key’ is the means by which you specify which value you want. The following two lines of code both show an example:
Entity e = context.InputParameters["Target"];
string name = e.Attributes["name"];  // Note that this is equivalent to: string name = e["name"];

In the first line, InputParameters is the dictionary, and "Target" is the key. In the second line, Attributes is the dictionary, and "name" is the key. The error ‘The given key is not present in the dictionary’ simply means that the dictionary does not have a value that corresponds to the key. So, this error would occur in the first line if InputParameters does not contain a key called "Target", or in the second line if there were no "name" in Attributes.

The way to avoid these errors is simple; test if the key exists before trying to use it. Different collection classes can provide different ways to perform this test, but the collection classes in the CRM SDK assemblies all inherit from an abstract DataCollection class that exposes a Contains method, so you can use a consistent approach across these collection classes.
if (context.InputParameters.Contains("Target"))
 Entity e = context.InputParameters["Target"];
 if (e.Attributes.Contains("name"))
  string name = e.Attributes["name"];

There are a few common reasons of the use of CRM collection classes where a key might not be present when you expect it:
  • Within a plugin, the values in context.InputParameters and context.OutputParameters depend on the message and the stage that you register the plugin on. For example, "Target" is present in InputParameters for the Create and Update messages, but not the SetState message. Also, OutputParameters only exist in a Post stage, and not in a Pre stage. There is no single source of documentation that provides the complete set of InputParameters and OutputParameters by message and stage, though this post provides a list of the most common ones for CRM 4, and most of these still apply in CRM 2011
  • The Attributes collection of an Entity will only contain values for attributes that have a value. You may get the Entity from a Retrieve or RetrieveMultiple having specified a ColumnSet with the attribute you want, but this attribute will not be present in the Attributes collection if there were no data in that attribute for that record
  • Within a plugin, the Attributes collection of an Entity that you obtain from the "Target" InputParameter will only contain attributes that were modified in the corresponding Create or Update method. Using the example above, if this were in a plugin registered on the Update message, the "name" attribute would only be present if the "name" attribute was changed as part of the Update; the "Target" InputParameter will not contain all the attributes for the entity