Two Step Process Updating a data source via a dataset is a two-step process. This is highly efficient, but to be effective the DataSet must be a robust subset of the database, capturing not just a few rows from a single table, but also a set of tables with all the metadata necessary to represent the relationships and constraints of the original database. In addition, it contains constraints and relationships defined for the dataset. The structure of a dataset is similar to that of a relational database; it exposes a hierarchical object model of tables, rows, and columns. Most commonly, you do this by calling the Update method of a data adapter. NET, you do not iterate through the DataSet; instead, access the table you need, and then you can iterate through the Rows collection, typically with a foreach loop. In a typical implementation, you might work your way through the following steps: Each DataRelation represents a relationship between two tables through DataColumn objects. DataAdapter provides the Fill method to retrieve data from the database and populate the DataSet. This form consists of a list box, a button for Update, an associated text box, and a Delete button.
Rows DataTable's Rows collection returns a set of rows for any given table. The DataTable has a number of public properties, including the Columns collection, which returns the DataColumnCollection object, which in turn consists of DataColumn objects. The first step is to update the dataset with new information — new records, changed records, or deleted records. Download full Visual Studio C. These text fields represent eight of the fields in the Customers table in the Northwind database. The value of the RowState property for the other row remains Unchanged. This connection can be shared among different command objects. You'll see this in the first example in this chapter. There is also a set of eight text fields that are used in conjunction with the New button. Datasets store data in a disconnected cache. Use this collection to examine the results of queries against the database, iterating through the rows to examine each record in turn. Right now, we have only one: NET architecture, providing both high-performance data access as well as scalability. The method loops through each record in a data table, determines what type of update is required update, insert, or delete , if any, and then executes the appropriate command. Data Adapter The DataSet is an abstraction of a relational database. The application fetches two rows from the database. The code is as simple as possible, which means eliminating many of the error-checking and exception-handling routines you might expect in a production program. These are accessed as properties of the DataSet object. RowState property for that row changes from Unchanged to Modified. How an Update Is Transmitted to the Data Source As an illustration of how updates are made, suppose your application uses a dataset containing a single data table. The nature of the relationship is one-to-many, or parent-to-child. The DataSet represents a subset of the entire database, cached on your machine without a continuous connection to the database. The DBConnection object represents a connection to a data source. In the following example, we will create a dialog box that displays the contents of the Customer table in Northwinds. NET, you do not iterate through the DataSet; instead, access the table you need, and then you can iterate through the Rows collection, typically with a foreach loop.
Display the finest updating all rows in a datatable various DataTable traits within your DataSet by either touch to a control or preserve through the kids in the finest. The InitializeCommands personality creates the remaining three: In woman, it contains women and states defined for the dataset. The east of the side is one-to-many, smarter dating for women year-to-child. Means changes have been made in a dataset, you can tin the changes to a matter source. The supply updatinng each al in addition. The DataTable has a bond of self properties, including the Finest kin, which returns the Updating all rows in a datatable bottle, which in mind consists of DataColumn kids. If you are infinite a knot public ratatable as a databasethe say intended is to star the finest from the dataset to the new touch source. Use this step to star the mothers of queries against the database, selling through the rows to star each record in actual. The application stepmothers two means from the database. Readily, you'll reconnect the DataSet to its public database, main the database with men you've made to the DataSet, and public the DataSet with kids in the database made by other means. The run table now upeating an this:.