TAILIEUCHUNG - Professional ASP.NET 1.0 Special Edition- P16

Professional Special Edition- P16:Those of us who are Microsoft developers can't help but notice that .NET has received a fair amount of visibility over the last year or so. This is quite surprising considering that for most of this period, .NET has been in its early infancy and beta versions. I can't remember any unreleased product that has caused this much interest among developers. And that's really an important point, because ignoring all the hype and press, .NET really is a product for developers, providing a great foundation for building all types of applications | now we can check if the values are valid If objRow ISBN 1999999999 Then Else End If then display the contents again To demonstrate the effect of the EndEdit method the next section of code just repeats the whole process - but this time it sets the value of the ISBN field to a number less than 1999999999 so that the test succeeds. This means that this time the EndEdit method is called. Again the contents of the table are displayed during and after the edit process The Original Current and Proposed Column Values If you were on your toes when reading the previous code listing you ll have seen that we used a special syntax when accessing the value of a column If objRow ISBN 1999999999 Then . As we ll see in more detail in the next chapter every column in every row of a table maintains three values for that item. These values are defined in the DataRowVersion enumeration and they are used to help maintain concurrency when updating data Original The value that was in the column when the DataTable was created and filled with data. It is compared to the value in the original database table when an update is performed to see if another user or process has changed the value since the DataTable data was created. Proposed The proposed value for this column after changes have been made following BeginEdit but before EndEdit J CancelEdit AcceptChanges or RejectChanges has been executed. Current The actual column value after changes have been made to it and after these changes have been accepted after EndEdit or AcceptChanges has been executed . The AcceptChanges and Rejectchanges methods are described next. Accepting and Rejecting Changes in a Row Table or DataSet As we saw earlier we can access any of the three values that are stored for every column in every row of a table at any time to get the appropriate value for a comparison test

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