If i go to washroom after the "Sehri" and i get late in washroom and the Azaan time happened and i haven't pray the "Sehri" Dua then what can i do? Can I pray Dua after coming out from washroom or when i am inside the washroom? please clear my problem.Thanks
What you call du'a is simply a wording to declare the intention to fast. Note that in some madhhabs it is sufficient to make it once in the beginning of Ramadan (for the whole month), but basically the intention is made in the mind and doesn't need to be uttered.
Finally be aware that the wording isn't correctly translated in your comment as:
"وَبِصَوْمِ غَدٍ نَّوَيْتُ مِنْ شَهْرِ رَمَضَانَ "
should be literally translated as
And with fasting tomorrow of the month Ramadan I intended
while one should rather say something like:
I intend to fast this day of Ramadan.
اني نويت صيام هذا اليوم من شهر رمضان
This is wrong from many perspectives: In fiqh niyyah must be uttered for an act that you are starting actually, so saying tomorrow (in Arabic غدا) you declare to fast another day as the niyyah must be uttered in the night and one rarely does suhur before midnight so it doesn't fit neither for the Islamic day which starts with maghrib nor for our 24h count. As you basically intend to fast the next day not the day that already started this should be evidence enough that this wording has no backup in the sunnah of our prophet (). Also the Arabic sentence is far away from being sound or close to what a fluent Arab would say to utter the niyyah among other issues it lacks the personal pronoun referring to oneself and an Arabic sentence starts either with a noun or verb which is not the case here.
Brother, Islam was made easy for you, so don't complicate it and make it hard for yourself. It says in the Quran in more than one place "I have made this religion easy for you..."
Do whatever you need to do in the bathroom. Your intention needs to be right (Allah Knows what is in your hearts). Like the brother said, make intention to keep a fast in your heart and mind. Then, when you come out of the bathroom, pray Fajir Namaaz as normal. There is nothing special about Fasting Namaaz or Dua. You can perform any Dua in any language you like. You make intention just before the fast begins or when it begins. Not a day/ a week or a month before. Our birth and death is in Allah's hands.