The first approach allows you to write portable code that can be applied to different data sources.
The second one gives quicker access to the values of cells.
In your original post you get the data from Text Box, of course it will be the new data, but it does not mean you have done the updating which means the data source of Grid View is still the old one.
You need to do updating first, and then rebind the Grid View and get the data source from Grid View, or you can get the Data Set directly as how you get the Data Set first time.
Also, I'm not using ajax to postback, I'm only posting the results back when the user is finished and clicks the submit button. What I'm trying to achieve is to display some rows to the user including a money value, then let the user add or subtract an amount to that value by putting the value to add in a textfield and clicking a button "add", which adds this amount to the money value.
I want to to this adding client side for efficiency.
How do I update the gridview's datasource (dataset) to match the newly (client side) altered values?
This topic consists of the following sub-topics: Returns the edit value within the currently focused cell. Get Row Cell Value methods can be identified by a specific Grid Column object or by a string that represents a column's field name. Get Row Cell Value method, you also need to identify the row that contains the desired cell. You can, for instance, handle this event if you need to synchronize other fields or controls with the changes made. Refer to the Validating Editors and Validating Rows documents for additional information.
The focused cell is identified by the focused column, which is specified by the Column View. If the cell isn't being edited, this property returns null (Nothing in Visual Basic). Is Editing property to determine whether a cell is currently being edited or not. The row is identified by a handle that represents the row's visual position within the View. If the values entered need to be validated, handle the validation events (Base View.
Focused Column property, and the focused row is specified by the Column View. To get the currently active editor, use the Base View. For more information on row handles, refer to the Identifying Rows and Cards document. Get Focused Data Row methods can be used if the View's data source is represented by a System.