Select the data from database

I need visual studio c# coding my doubt is how to select data from sqlserver below the example model

My form is this

i need to select from database when i select author in combobox that related data display in next combobox i.e Bookname

when i select author that related bookname display in combo box my database model is below the picture

for example i select author name like "Balaguruswamy" i want display "Bookname" related from balaguruswamy i.e. java,C++,C these bookname will display in Combobox then i will select anyone display whole data

please help i need c# , sqlserver coding...

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karthik