Updating database using table adapter

Question

i have used the following code to update the database
studentbindingsource.Endedit();
studenttableadapter.update();
I am getting an error:"Set update command for the table adapter"
The table adapter is creating the select and insert command automatically as it is supposed to but the update command is not created .
In that case i have to explicitly write the update command , but i want to know where i am going wrong..Please help me with ur answers..