VB.Net DataTable.Clone Method (System.Data)

By: Rajesh P.S.

In VB.NET, you can use the DataTable.Clone method to create a new DataTable that has the same structure as an existing DataTable, including columns, constraints, and primary keys. However, unlike DataTable.Copy, the Clone method does not copy the data itself. It's useful when you want to work with a new DataTable that has the same structure as the original but does not share data.

DataTable.Clone()

The Clone method creates a shallow copy of the DataTable's structure. Here's an example:

' Create a sample DataTable Dim originalTable As New DataTable() originalTable.Columns.Add("ID", GetType(Integer)) originalTable.Columns.Add("Name", GetType(String)) ' Define a primary key constraint on the original table originalTable.PrimaryKey = New DataColumn() {originalTable.Columns("ID")} ' Create a clone of the original table Dim clonedTable As DataTable = originalTable.Clone() ' Check if the cloned table has the same structure as the original table Console.WriteLine($"Number of columns in cloned table: {clonedTable.Columns.Count}") Console.WriteLine($"Does the cloned table have a primary key constraint? {clonedTable.PrimaryKey.Length > 0}")

In this example, the clonedTable has the same structure as the originalTable, including columns and constraints, but it does not contain any data.

Copying Data Manually

To create a deep copy of the original table that includes the data, you need to create a new DataTable using Clone and then manually copy the data from the original table:

' Create a deep copy with data Dim deepCopyTable As DataTable = originalTable.Clone() For Each originalRow As DataRow In originalTable.Rows Dim newRow As DataRow = deepCopyTable.NewRow() newRow.ItemArray = originalRow.ItemArray deepCopyTable.Rows.Add(newRow) Next

This code creates a deep copy (deepCopyTable) that includes both the structure and data from the originalTable.

You can use cloned DataTables in a variety of ways. For example, you can use a cloned DataTable to create a new DataTable that is populated with data from another source. You can also use a cloned DataTable to create a new DataTable that contains a subset of the data from the original DataTable.

Here are some examples of how to use cloned DataTables:

Populated with data from a database

Create a new DataTable that is populated with data from a database:

Imports System.Data Imports System.Data.SqlClient Public Class Example Public Sub Main() ' Create a new SqlConnection object. Dim connection As New SqlConnection("Data Source=(local);Initial Catalog=AdventureWorks2019;Integrated Security=True") ' Create a new SqlCommand object. Dim command As New SqlCommand("SELECT Name, Age FROM Person.Person", connection) ' Open the connection. connection.Open() ' Create a new DataAdapter object. Dim adapter As SqlDataAdapter = New SqlDataAdapter(command) ' Fill a new DataTable object with the data from the database. Dim dataTable As New DataTable() adapter.Fill(dataTable) ' Clone the DataTable. Dim cloneDataTable As DataTable = dataTable.Clone() ' Close the connection. connection.Close() ' Use the cloned DataTable. End Sub End Class

Subset of the data from the original DataTable

Create a new DataTable that contains a subset of the data from the original DataTable:

Imports System.Data Public Class Example Public Sub Main() ' Create a new DataTable object. Dim dataTable As New DataTable() ' Add some columns to the DataTable. dataTable.Columns.Add("Name") dataTable.Columns.Add("Age") ' Add some data to the DataTable. Dim row1 As DataRow = dataTable.NewRow() row1("Name") = "John Doe" row1("Age") = 30 dataTable.Rows.Add(row1) Dim row2 As DataRow = dataTable.NewRow() row2("Name") = "Jane Doe" row2("Age") = 25 dataTable.Rows.Add(row2) ' Clone the DataTable. Dim cloneDataTable As DataTable = dataTable.Clone() ' Add a subset of the data from the original DataTable to the cloned DataTable. Dim rows As DataRow() = dataTable.Select("Age > 25") For Each row In rows cloneDataTable.Rows.Add(row) Next ' Use the cloned DataTable. End Sub End Class

Use Cases

The Clone method is useful when you want to maintain the same structure as the original DataTable, such as columns and constraints, while working with a new DataTable that does not share data. It is commonly used when you need to create a clean slate for data manipulation without altering the original data.

Keep in mind that Clone is primarily for creating a new table with the same structure. If you need to create a copy that includes data as well, you can use Clone in combination with manually copying data, as shown in the examples above.

Conclusion

The DataTable.Clone method is used to create a new DataTable with the same structure as an existing DataTable, including columns, constraints, and primary keys, but it does not include data. It's typically used when you need to work with a new DataTable that has the same structure as the original but does not share the same data. If you want to create a deep copy that includes data, you can use DataTable.Clone in combination with manually copying the data.

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