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Determining Dataset States

The state—or mode—of a dataset determines what can be done to its data. For example, when a dataset is closed, its state is dsInactive, meaning that nothing can be done to its data. At runtime, you can examine a dataset's read-only State property to determine its current state. The following table summarizes possible values for the State property and what they mean:  

Values for the dataset State property  

Value 
State 
Meaning 
dsInactive  
Inactive  
DataSet closed. Its data is unavailable.  
dsBrowse  
Browse  
DataSet open. Its data can be viewed, but not changed. This is the default state of an open dataset.  
dsEdit  
Edit  
DataSet open. The current row can be modified. (not supported on unidirectional datasets)  
dsInsert  
Insert  
DataSet open. A new row is inserted or appended. (not supported on unidirectional datasets)  
dsSetKey  
SetKey  
DataSet open. Enables setting of ranges and key values used for ranges and GotoKey operations. (not supported by all datasets)  
dsCalcFields  
CalcFields  
DataSet open. Indicates that an OnCalcFields event is under way. Prevents changes to fields that are not calculated.  
dsCurValue  
CurValue  
DataSet open. Indicates that the CurValue property of fields is being fetched for an event handler that responds to errors in applying cached updates.  
dsNewValue  
NewValue  
DataSet open. Indicates that the NewValue property of fields is being fetched for an event handler that responds to errors in applying cached updates.  
dsOldValue  
OldValue  
DataSet open. Indicates that the OldValue property of fields is being fetched for an event handler that responds to errors in applying cached updates.  
dsFilter  
Filter  
DataSet open. Indicates that a filter operation is under way. A restricted set of data can be viewed, and no data can be changed. (not supported on unidirectional datasets)  
dsBlockRead  
Block Read  
DataSet open. Data-aware controls are not updated and events are not triggered when the current record changes.  
dsInternalCalc  
Internal Calc  
DataSet open. An OnCalcFields event is underway for calculated values that are stored with the record. (client datasets only)  
dsOpening  
Opening  
DataSet is in the process of opening but has not finished. This state occurs when the dataset is opened for asynchronous fetching.  

Typically, an application checks the dataset state to determine when to perform certain tasks. For example, you might check for the dsEdit or dsInsert state to ascertain whether you need to post updates.

Note: Whenever a dataset's state changes, the OnStateChange event is called for any data source components associated with the dataset. For more information about data source components and OnStateChange, see Responding to Changes Mediated by the Data Source.

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