Automate tab or cBot build errors in cTrader

What is causing it

A code error or an outdated cAlgo API reference.

Why this happens

cTrader compiles cBots and indicators from C# source into runnable code, and a build failure means the compiler rejected the source rather than the platform being at fault. The cTrader Automate API has changed across major versions, with names and namespaces altered, so code written for an earlier version will not build against the current one. Anything sourced from an older forum post or tutorial is likely to fail for exactly this reason.

The compiler reports errors in the order it encounters them, and in C# one genuine mistake often produces several downstream complaints. The first error in the list is usually the real one and the rest are consequences, so fixing the first and rebuilding frequently clears most of the list at once.

The fix, step by step

1. Open the cBot in the Automate editor and read the build error.
2. Update deprecated cAlgo or cTrader Automate API calls.
3. For a third-party cBot, get the latest version from the author.
4. Rebuild after fixing, and check the log for remaining errors.

How to confirm it is fixed

A successful build reports no errors and the cBot or indicator becomes available to add. Attach it, start it, and watch its log for the first few bars, because building successfully only proves it compiles, not that it runs correctly. A runtime error will appear in the log after it starts rather than at build time.

Stopping it happening again

Take cBots and indicators from their original published source so you get the maintained version rather than an old copy. Note which API version a piece of code targets before editing it. When writing your own, build after each small change so it is obvious which change introduced the error.