To get Tables count in ax 2012 you can write below code .
treenode::findNode('\\Data Dictionary\\Tables').AOTchildNodeCount()
You can check this code in info message by job.
Problem: On click sales order Totals option getting below error. Please help me how to solve it. Microsoft.Dynamics.Ax.Xpp.ClrErrorException: Exception of type 'Microsoft.Dynamics.Ax.Xpp.ClrErrorException' was thrown. at Microsoft.Dynamics.Ax.Xpp.CLRInterop.MakeReflectionCall(Object instance, String methodName, Object[] parameters) at Dynamics.Ax.Application.TaxDocumentProxy.Sumbytaxaccountingprovider(TaxAccountingProvider taxAccountingProvider, TaxAcctPostingProfDistributionSide postingSide, String taxType, String taxComponent, Boolean , Boolean , Boolean ) in TaxDocumentProxy.sumByTaxAccountingProvider.xpp:line 15 at Dynamics.Ax.Application.TaxDocumentProxy.@Sumbytaxaccountingprovider(TaxAccountingProvider taxAccountingProvider, TaxAcctPostingProfDistributionSide postingSide, String _taxType, Boolean , Boolean ) at Dynamics.Ax.Application.TaxDocumentProxy.@Sumbytaxaccountingprovider(TaxAccountingProvider taxAccountingProvider, TaxAcctPostingProfDistributionSide postingSide, ...