The syntax of the Update Statement is ok.
But you must double apostrophes in strings of each textbox
For example:
if in a textbox there is the string -> ab'cd
you must write in the SQL Query the string -> ab''cd
You can use the function:
Protected Function CheckSqlStr(ByVal sParam As String) As String
Dim sRet As String
sRet = Replace(sParam, "'", "''")
CheckSqlStr= sRet
End Function
and use it in the SQL Query
sqlupdate = "UPDATE Customer_Master SET Names='" & CheckSqlStr(txtname.Text) & "', Address='" & CheckSqlStr(txtaddr.Text) & "', PhoneNo='" & CheckSqlStr(txtphno.Text) & "' WHERE CustomerID='" & CheckSqlStr(txtcid.Text) & "'"