TryGetOriginalValue Method

Overview

The TryGetOriginalValue method allows you to get the baseline (original) value for the specified column from the row’s original-values snapshot, if such a snapshot exists. Original values are captured automatically when an Unchanged row is modified for the first time or when the Delete method is called.

The method returns true when a snapshot exists and contains the specified column; otherwise it returns false and outputs null.

Namespace and Assembly

Namespace: PocoDataSet.ObservableData
Assembly: PocoDataSet.ObservableData.dll

Usage Example

// 1. Create observable data set
IObservableDataSet observableDataSet = new ObservableDataSet();

// 2. Create Department observable table
IObservableDataTable departmentObservableDataTable = observableDataSet.AddNewTable("Department");
departmentObservableDataTable.AddColumn("Id", DataTypeNames.INT32);
departmentObservableDataTable.AddColumn("Name", DataTypeNames.STRING);

// 3. Add tow observable data rows in Unchanged state to Department observable table
IObservableDataRow departmentObservableDataRow1 = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow1["Id"] = 1;
departmentObservableDataRow1["Name"] = "Marketing";
departmentObservableDataRow1.AcceptChanges();

IObservableDataRow departmentObservableDataRow2 = departmentObservableDataTable.AddNewRow();
departmentObservableDataRow2["Id"] = 2;
departmentObservableDataRow2["Name"] = "Reception";
departmentObservableDataRow2.AcceptChanges();

// 4. Try to read the original value before any modification or deletion.
// No snapshot exists yet, so the method returns false.
object? departmentName = null;
departmentObservableDataRow1.TryGetOriginalValue("Name", out departmentName);
departmentObservableDataRow2.TryGetOriginalValue("Name", out departmentName);

// 6. Call Delete method to put the first row into Deleted state
departmentObservableDataRow1.Delete();

// 7. Update value of the second row to put it into Modified state
departmentObservableDataRow2["Name"] = "HR";

// 8. Call TryGetOriginalValue method to get cached "Marketing" value for the Name column
bool hasOriginalName1 = departmentObservableDataRow1.TryGetOriginalValue("Name", out departmentName);

// 9. Call TryGetOriginalValue method to get cached "Reception" value for the Name column
bool hasOriginalName2 = departmentObservableDataRow2.TryGetOriginalValue("Name", out departmentName);

 

Table of Content POCO DataSet API References ObservablePOCO DataSet Types ObservableDataRow Members

 

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Business Process Programming in .Net
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