Refreshing UI Data Without Losing Edits – Quick Start

Many applications need to refresh data from the server while the user is actively editing. POCO DataSet supports this scenario by using IObservableDataSet.DoRefreshMergePreservingLocalChanges merge: refreshed server values are applied to clean rows, while local edits remain untouched.

When to use merge which preserves local changes

• You want to update the UI with newer server values.
• You must not overwrite in-progress user edits.
• You want new server rows to appear without discarding local changes.

What merge, which preserves local changes, guarantees

• Unchanged rows may be updated from the refreshed snapshot.
• Added, Modified, and Deleted rows are preserved (not overwritten).
• New rows from the refreshed snapshot are added as Unchanged.
• Rows missing from the refreshed snapshot may be removed only when the current row is Unchanged (unless the table is excluded from deletion).

Core workflow

1. Keep a UI-bound observabl edataset in memory.
2. Request a refreshed dataset snapshot from the server.
3. Merge the refreshed snapshot into the current dataset by using IObservableDataSet.DoRefreshMergePreservingLocalChanges method.
4. UI updates for clean rows; dirty rows remain dirty and unchanged.

Minimal working example

Assuming observable data set is used for UI binding, for example:

// 1. Create observable dataset
IObservableDataSet boundObservableDataSet = new ObservableDataSet();

// 2. Add Department table to the observable dataset
IObservableDataTable departmentObservableDataTable = boundObservableDataSet.AddNewTable("Department");
departmentObservableDataTable.AddColumn("Id", DataTypeNames.INT32);
departmentObservableDataTable.AddColumn("Name", DataTypeNames.STRING);

// 3. Add a row to the Department table (data row state is Added)
IObservableDataRow departmentObservableDataRow = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow["Id"] = 1;
departmentObservableDataRow["Name"] = "Sales";

// 4. Add another row to the Department table, the values of which user hadn't cahnged (data row state is Unchanged)
IObservableDataRow departmentObservableDataRow = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow["Id"] = 2;
departmentObservableDataRow["Name"] = "Emergency";
departmentObservableDataRow.AcceptChanges();
// The following line is a pseudo-code example of how UI can be bound to the observable data set.
// The actual binding code depends on the UI framework and is not part of POCO DataSet.
somePage.DataContext = boundObservableDataSet;

Assuming user clicked on Refresh button asking to refresh bound data. The following code imitates the server response.

// 1. Create refreshed dataset
IDataSet refreshedDataSet = DataSetFactory.CreateDataSet();

// 2. Add Department table to the refreshed dataset
IDataTable departmentRefreshedDataTable = refreshedDataSet.AddNewTable("Department");
departmentRefreshedDataTable.AddColumn("Id", DataTypeNames.INT32);
departmentRefreshedDataTable.AddColumn("Name", DataTypeNames.STRING);

// 3. Add two rows to the Department table which imitate changed data in the database
IDataRow departmentRefreshedDataRow = departmentRefreshedDataTable.AddNewRow();
departmentRefreshedDataRow["Id"] = 1;
departmentRefreshedDataRow["Name"] = "Sales and Marketing";

departmentRefreshedDataRow = departmentRefreshedDataTable.AddNewRow();
departmentRefreshedDataRow["Id"] = 2;
departmentRefreshedDataRow["Name"] = "Emergency Department";

// 4. Mark all rows as Unchanged to indicate they are clean server values
refreshedDataSet.AcceptChanges();

Call IObservableDataSet.DoRefreshMergePreservingLocalChanges method to merge refreshed snapshot into the current dataset while preserving local changes:

IObservableMergeOptions observableMergeOptions = new ObservableMergeOptions();
boundObservableDataSet.DoRefreshMergePreservingLocalChanges(refreshedDataSet, MergeMode.Refresh);

// Observe that the name of the Sales department is not overwridden because the observable row state is Added
string nameOfSalesDepartment = (string)currentDepartment.Rows[0]["Name"];

// Observe that the name of the Emergency department is updated to "Emergency Department" because the observable row state is Unchanged
string nameOfEmergencyDepartment = (string)currentDepartment.Rows[1]["Name"];

 

Table of Content POCO DataSet Quick Start

 

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Business Process Programming in .Net
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