Download the Microsoft Dynamics CRM 2013 Custom Code Validation Tool.
Several things have changed or will change soon.
For people using Microsoft Dynamics CRM 2011 on-premises who still haven’t applied the December 2012 Service Update:
For people looking to upgrade to Microsoft Dynamics CRM 2013, these changes and others were announced on this page: What’s Changing in the Next Major Release.
The support team did some research on common issues that could break and prepared a Microsoft Dynamics CRM 2013 Custom Code Validation Tool. Download this tool and extract the contents. Within the contents you will find instructions about how to install and use the tool.
If you have downloaded this tool and used it before, you will see that it now includes additional logic to check for changes related to upgrading to Microsoft Dynamics CRM 2013.
The tool is a managed solution that you install and it will examine your web resources and show you where there might be some problem areas.
Note: Not every issue that is returned by this tool represents a problem. This tool looks for certain characters in the code and highlights those that look like they may be a problem. But there are many times where it is perfectly fine to use certain code in one situation if you have applied the appropriate code for a different situation.
This tool can’t find every possible problem. You still need to do testing as part of your upgrade process to ensure that everything works. Use this tool to get a sense of what kind of issues exist and identify which web resources need the most attention.
If the code is part of a solution created by someone else which you installed, for example maybe you downloaded it from the marketplace, then you should contact the people who created the solution. They may have already created an updated version that can work with the newer versions of Microsoft CRM.
If your code was applied by a partner who helped you with your implementation, reach out to them and discuss the results you get when you run using the Custom Code Validation tool.
To summarize the types of changes that need to be made:
Using CRM 4.0 (2007) endpoints
Using CRM 4.0 form object model (crmform)
Code is not ready for browsers other than Internet Explorer
Code uses unsupported methods
If there isn't a supported way to achieve your requirement you will need to consider dropping functionality it provides or finding another way to achieve it.
Here are some links that can provide tips that may be useful when fixing your code:
It really depends on what version you plan to upgrade to.
Excellent blog !