How to: Check for Changed Rows

When changes are made to records in a dataset, information about those changes is stored until you commit them. Changes are committed when calling the AcceptChanges method of a dataset, data table, or calling the Update method of a TableAdapter or data adapter.

Changes are tracked in each data row two ways:

• Each data row contains information as to it's RowState (for example, Added, Modified, Deleted, Unchanged).

• Each changed data row contains multiple versions of that row (DataRowVersion); the original (before changes), and current (after changes) versions — that you can access. During the period when a change is pending (the time that you can respond to the RowChanging event), a third version — the proposed version— is available as well. For more information, see How to: Get Specific Versions of a DataRow.

Determining If There Are Changed Rows

The HasChanges method of a dataset returns true if changes have been made in the dataset. After determining that changed rows exist, you can call the GetChanges method of a DataSet or DataTable to return a set of changed rows. For more information, see How to: Retrieve Changed Rows.

To determine if any changes have been made to any rows

• Call the HasChanges method of a dataset to check for changed rows.

  The following example shows how to check the return value from the HasChanges method to detect whether there are any changed rows in a dataset named NorthwindDataset1.

  If NorthwindDataSet1.HasChanges() Then 
  
      ' Changed rows were detected, add appropriate code. 
  Else 
      ' No changed rows were detected, add appropriate code.  
  End If
  

  if (northwindDataSet1.HasChanges()) 
  {
      // Changed rows were detected, add appropriate code.
  }
  else
  {
      // No changed rows were detected, add appropriate code.
  }
  

Determining the Type of Changes

You can also check to see what type of changes have been made in a dataset by passing a value from the DataRowState enumeration to the HasChanges method.

To determine what type of changes have been made to a row

• Pass a DataRowState value to the HasChanges method.

  The following example shows how to check a dataset named NorthwindDataset1 to determine if there have been any new rows added to it:

  If NorthwindDataSet1.HasChanges(DataRowState.Added) Then 
  
      ' New rows have been added to the dataset, add appropriate code. 
  Else 
      ' No new rows have been added to the dataset, add appropriate code. 
  End If
  

  if (northwindDataSet1.HasChanges(DataRowState.Added)) 
  {
      // New rows have been added to the dataset, add appropriate code.
  }
  else
  {
      // No new rows have been added to the dataset, add appropriate code.
  }
  

See Also

Concepts

What's New in Data

Displaying Data Overview

Other Resources

Editing Data in Your Application

Data Walkthroughs

Connecting to Data in Visual Studio

Preparing Your Application to Receive Data

Fetching Data into Your Application

Displaying Data on Forms in Windows Applications

Validating Data

Saving Data