I have one Database ,in which there is one table employee .I want to fetch data from table Department and want to display in combobox cmbDept.

If the only table is employee, you'll have a lot of trouble fetching data from one named Department.

(Note: Punctuation follows immediately after the word, then a space, then the rest of the sentence. I have noticed that most individuals who post from India invert that, with word, then space, then punctuation. Is there a reason stemming from the native language/text that is used in India?)

dim conn as new sqlclient.sqlconnection
dim cmd as new sqlclient.sqlcommand
dim dr as sqlclient.sqldatareader
//define above code globely//

form_load event()
conn.connectionstring="type your connection string here"
cmd.connection=conn
conn.open()
cmd.commandtext="select * from employee"
combobox1.items.clear
combobox1.items.add("")
dr=cmd.executeReader
while dr.read()
combobox1.items.add(dr(0))
end while
dr.close
conn.close
//plz type this code on form load event and tyr//

imports system.data.oledbclient
dim conn as new oledbclient.oledbconnection
dim cmd as new oledbclient.oledbcommand
dim dr as oledbclient.oledbdatareader
//define above code globely//

form_load event()
conn.connectionstring="type your connection string here"
cmd.connection=conn
conn.open()
cmd.commandtext="select * from employee"
combobox1.items.clear
combobox1.items.add("")
dr=cmd.executeReader
while dr.read()
combobox1.items.add(dr(0))
end while
dr.close
conn.close
//plz type this code on form load event and tyr//

If you have an OleDb Connection :

Dim daEmp as New OleDb.OleDbDataAdapter("SELECT employee FROM Department", connEmp)
Dim dsEmp as New DataSet
daEmp.Fill(dsEmp,"EmpTable")
Dim rowEmp as DataRow
For Each rowEmp in dsEmp.Tables("EmpTable").Rows
   cmbDept.Items.Add(rowEmp("employee"))
Next

That would populate the ComboBox with the Employee data in the Department table.

Hope it helps you :)