Applying validation on fields (methods) in dialog form in Ax 2012

1. go to class declaration and make the following "FormBulidStringControl"

FormBuildStringControl                  controlFromDataAreaId,controlToDataAreaId,controlGeneralType,controlMainAccounts,controlDivision;

2. now in the "dialog" method write the following method,below the field where we enter value

controlFromDataAreaId = dlgFromDataAreaId.control();

3. now in the ""dialogPostRun" method write the following code

controlFromDataAreaId.registerOverrideMethod(methodStr(FormStringControl,Validate),

                                            methodStr(TTC_EOM,fromtoEntity_Validate),

                                            this);

4. now make a new method, in this case ""fromtoEntity_Validate

public boolean fromtoEntity_Validate(FormStringControl  _control)

{

    boolean ret         = _control.validate();

    select DataArea from companyInfo

        where companyInfo.DataArea  == _control.valueStr();

    if(companyInfo)

    {

        ret = true;

    }

    else

    {

        ret = ret && checkFailed("Entity does not exist");

    }

    return ret;

}