TeamCity share build number between multiple build configurations

Solution 1:

If one of build configurations A has snapshot or artifact dependency on build configuration B, then you can obtain build number from B in A with help of dependency parameter:

%dep.<B id>.build.number%

Where <B id> is id of build configuration B (see buildTypeId parameter in URL).

Solution 2:

This solution works for me:

1. Create Build Configuration. Let say "GenerateBuildNumber", do not attach template. Do not specify any build steps. Click Save.
2. Edit configuration for your project. Go to "Build Configuration Settings->Dependencies". Click "Add new snapshot dependecy".
3. Select previously created "GenerateBuildNumber" in "Depend on" section. Uncheck option "Do not run new build if there is a suitable one". Click Save.
4. Go to "General Settings", clear "Build number format:", click the button on the left side with 3 lines. Select "%dep.YouProjName_GenerateBuildNumber.env.BUILD_NUMBER%". Click Save.

Run your project build. Firstly it should start "GenerateBuildNumber" project then your project with a generated number. Do the steps 2-4 for every project you want to have unique generated number. Profit!