HomeSearch

VB.NET DataRow Examples

Use the DataRow type to store values in a row in a DataTable. Use the ItemArray property.
DataRow. A DataRow contains an individual row of data. It narrows the data abstraction to the level of the row. The DataRow type provides ways to add, remove, or read cells from the enclosing data structure.
Example. As we begin, please notice that the examples that follow invoke a function called GetTable. This function returns a fully formed DataTable instance. It has four columns and five rows, for a total of 20 cells.DataTable

Tip: You can paste this function into the following examples to achieve compilation.

VB.NET program that creates DataTable instance Module Module1 Function GetTable() As DataTable ' Generate a new DataTable. ' ... Add columns. Dim table As DataTable = New DataTable table.Columns.Add("Weight", GetType(Integer)) table.Columns.Add("Name", GetType(String)) table.Columns.Add("Breed", GetType(String)) table.Columns.Add("Date", GetType(DateTime)) ' ... Add rows. table.Rows.Add(57, "Koko", "Shar Pei", DateTime.Now()) table.Rows.Add(130, "Fido", "Bullmastiff", DateTime.Now()) table.Rows.Add(92, "Alex", "Anatolian Shepherd Dog", DateTime.Now()) table.Rows.Add(25, "Charles", "Cavalier Kind Charles Spaniel", DateTime.Now()) table.Rows.Add(7, "Candy", "Yorkshire Terrier", DateTime.Now()) Return table End Function Sub Main() ' Acquire the DataTable instance. Dim table As DataTable = GetTable() End Sub End Module
Create. We see a simple way to construct a DataRow instance using an Object array. When you create the Object array, please set it up so that the elements are arranged to match the ordering of the DataRow template itself.

Next: Invoke the Add method upon the Rows collection to turn the Object array into part of the enclosing DataTable structure.

VB.NET program that adds DataRow Module Module1 Sub Main() Dim table As DataTable = GetTable() ' Create an array of four objects and add it as a row. Dim v(3) As Object v(0) = 7 v(1) = "Candy" v(2) = "Yorkshire Terrier" v(3) = DateTime.Now() table.Rows.Add(v) End Sub End Module
Get. It is useful to acquire references to individual DataRow instances from the DataTable based on indexes. Once you acquire the DataRows, you can access cells from those rows using indexes or string indexers.

Here: In this example, we access the first and last row from the DataRow, and then look up a cell on those rows.

VB.NET program that accesses rows Module Module1 Sub Main() Dim table As DataTable = GetTable() ' First row. Dim row1 As DataRow = table.Rows(0) Console.WriteLine(row1("Breed")) ' Last row. Dim row2 As DataRow = table.Rows(table.Rows.Count - 1) Console.WriteLine(row2("Breed")) End Sub End Module Output Shar Pei Yorkshire Terrier
Loop. How can you loop through the cells in a DataRow? You can use the ItemArray instance property upon the row instance. On the iteration variable in the For-Each loop, please notice that you must test the type of the Object.

And: After this, you could perform more specific operations based on that type.

VB.NET program that loops through row Module Module1 Sub Main() Dim table As DataTable = GetTable() ' Get first row. Dim row1 As DataRow = table.Rows(0) ' Loop over ItemArray. For Each item As Object In row1.ItemArray ' Test the type of each element. If (TypeOf item Is Integer) Then Console.WriteLine("Integer") ElseIf (TypeOf item Is String) Then Console.WriteLine("String") ElseIf (TypeOf item Is DateTime) Then Console.WriteLine("DateTime") End If Next End Sub End Module Output Integer String String DateTime
Remove. Sometimes you want to remove a row from an enclosing DataTable, but not actually erase that row's data from memory. You can therefore remove a row and then add it somewhere else. To do this, use the Remove Sub.

Here: This example demonstrates that when you remove the first row, the DataTable changes so that the second row is in the first position.

VB.NET program that removes rows Module Module1 Sub Main() ' Get the DataTable. Dim table As DataTable = GetTable() ' Get the first row. Dim row As DataRow = table.Rows(0) table.Rows.Remove(row) ' Get the new first row. row = table.Rows(0) Console.WriteLine(row("Name")) End Sub End Module Output Fido
Delete. Delete actually clears the memory inside the DataRow instance you call it upon. In other words, this will yield an empty or null row. And it will remove the row from the previously enclosing DataTable structure.Nothing
VB.NET program that deletes rows Module Module1 Sub Main() ' Get the DataTable. Dim table As DataTable = GetTable() ' Get the first row and delete it. Dim row As DataRow = table.Rows(0) row.Delete() ' Get the new first row. row = table.Rows(0) Console.WriteLine(row("Name")) End Sub End Module Output Fido
Field. How can you get a field from a DataRow? You can use the Field extension. This eliminates the need to cast the object returned—it is a strongly-typed Function. It has a different syntax form.DataRow Field
Summary. The DataRow provides a necessary level of abstraction for manipulating the DataTable structure. As an essential type for developing data-driven VB.NET programs, the DataRow is easy to use once the underlying concepts are understood.
© 2007-2020 Sam Allen. Every person is special and unique. Send bug reports to info@dotnetperls.com.
Home
Dot Net Perls