MergeWith Method

Overview

The MergeWith method merges data from a refreshed (non-observable) IDataSet into the current observable data set (IObservableDataSet). It delegates the merge process to an observable merge handler selected from IObservableMergeOptions.

This method is commonly used in two scenarios:

Refresh merge: merge data received from an external source (database / service) into an existing observable data set. This is typically used during the data search action to refresh UI-bound data after reloading from the database.
Post-save merge: merge server-returned values (identity columns, rowversion, computed fields) into the observable data set after a successful save (when using MergeMode.PostSave in the observable merge options).

Declaration

/// <summary>
/// Merges observable data set with data from refreshed data set
/// </summary>
/// <param name="currentObservableDataSet">Current observable data set</param>
/// <param name="refreshedDataSet">Refreshed data set</param>
/// <param name="observableMergeOptions">Observable merge options</param>
public static IObservableDataSetMergeResult MergeWith(this IObservableDataSet? currentObservableDataSet, IDataSet? refreshedDataSet, IObservableMergeOptions? observableMergeOptions = null)

Namespace and Assembly

Namespace: PocoDataSet.ObservableExtensions
Assembly: PocoDataSet.ObservableExtensions.dll

Usage Example

The following examples demonstrate both Refresh and PostSave merge scenarios for observable data sets.

Example 1 - Refresh Mode

// 1. Create observable data set with a newly added row (client-side)
IObservableDataSet currentObservableDataSet = new ObservableDataSet();

IObservableDataTable departmentObservableDataTable = currentObservableDataSet.AddNewTable("Department");
departmentObservableDataTable.AddColumn("Id", DataTypeNames.INT32);
departmentObservableDataTable.AddColumn("Name", DataTypeNames.STRING);

IObservableDataRow departmentObservableDataRow = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow["Id"] = 1;
departmentObservableDataRow["Name"] = "Sales";
departmentObservableDataRow.AcceptChanges(); // put row into Unchanged state

// 2. Create a refreshed data set returned from database / service (non-observable)
IDataSet refreshedDataSet = DataSetFactory.CreateDataSet();
IDataTable departmentRefreshedDataTable = refreshedDataSet.AddNewTable("Department");
departmentRefreshedDataTable.AddColumn("Id", DataTypeNames.INT32);
departmentRefreshedDataTable.AddColumn("Name", DataTypeNames.STRING);

IDataRow departmentRefreshedDataRow = departmentRefreshedDataTable.AddNewRow();
departmentRefreshedDataRow["Id"] = 1;
departmentRefreshedDataRow["Name"] = "Sales and Marketing";

// 3. Merge refreshed values into the current observable data set (Refresh mode)
IObservableMergeOptions observableMergeOptions = new ObservableMergeOptions();
observableMergeOptions.MergeMode = MergeMode.Refresh;

IObservableDataSetMergeResult mergeResult = currentObservableDataSet.MergeWith(refreshedDataSet, observableMergeOptions);

// 4. Current observable row now has refreshed values "Sales and Marketing"
string? name = (string?)departmentObservableDataTable.Rows[0]["Name"];

Example 2 - PostSave Mode

Post-save merge is typically used immediately after saving a changeset to the database. The database may generate or update values such as identity keys, rowversion, computed columns, or trigger-populated fields.

// 1. Create observable data set with a newly added row (client-side)
IObservableDataSet observableDataSet = new ObservableDataSet();

IObservableDataTable departmentObservableDataTable = observableDataSet.AddNewTable("Department");
departmentObservableDataTable.AddColumn("Id", DataTypeNames.INT32); // identity in DB
departmentObservableDataTable.AddColumn("Name", DataTypeNames.STRING);
departmentObservableDataTable.AddColumn("RowVersion", DataTypeNames.BINARY); // rowversion/timestamp in DB

IObservableDataRow departmentObservableDataRow = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow["Name"] = "Engineering";

// At this moment the row is typically in Added state and has no identity / rowversion yet.
// Get correlation data from row
Guid clientKey = departmentObservableDataRow.GetDataFieldValue<Guid>(SpecialColumnNames.CLIENT_KEY);

// 2. Build a server-returned data set after save
// This data set contains the database-generated values for the same logical row.
IDataSet postSaveDataSet = DataSetFactory.CreateDataSet();
IDataTable postSaveDepartmentDataTable = postSaveDataSet.AddNewTable("Department");
postSaveDepartmentDataTable.AddColumn("Id", DataTypeNames.INT32);
postSaveDepartmentDataTable.AddColumn("Name", DataTypeNames.STRING);
postSaveDepartmentDataTable.AddColumn("RowVersion", DataTypeNames.BINARY);

IDataRow postSaveDepartmentDataRow = postSaveDepartmentDataTable.AddNewRow();
postSaveDepartmentDataRow["Id"] = 10; // Imitate identity generated by DB
postSaveDepartmentDataRow["Name"] = "Engineering";
postSaveDepartmentDataRow["RowVersion"] = new byte[] { 1, 0, 0, 0, 0, 0, 0, 0 };

// Imitate correlation between observable and saved rows
postSaveDepartmentDataRow[SpecialColumnNames.CLIENT_KEY] = clientKey;

// 3. Merge server-returned values into the observable data set using PostSave mode
IObservableMergeOptions observableMergeOptions = new ObservableMergeOptions();
observableMergeOptions.MergeMode = MergeMode.PostSave;

IObservableDataSetMergeResult mergeResult = observableDataSet.MergeWith(postSaveDataSet, observableMergeOptions);

// 4. Current row now has server-generated values (identity/rowversion) and is typically accepted as Unchanged by the merge handlers
int id = departmentObservableDataTable.Rows[0].GetDataFieldValue<int>("Id"); // 10
byte[]? rowVersion = departmentObservableDataTable.Rows[0].GetDataFieldValue<byte[]>("RowVersion");

Notes

The detailed merge rules (primary key matching, deletions, schema evolution, exclusions, and post-save propagation) are implemented by the observable merge handlers, not by this method itself.
If you call MergeWith repeatedly with the same IObservableMergeOptions instance, the method clears the previous result before merging so the returned merge result always describes the most recent merge.

Table of Content POCO DataSet Observable Data Set Members

Business Process Programming in .Net
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