Roy,
what you have to do is to focus on the DataRow collection, as a (single) DataColumn represents the Type of Data which is stored in your Table. I'm sure you won't be surprised when I tell you that a DataRow itself consists of a collection of DataItems which represent the actual values in a table.
Imagine the following:
ID | Name | Comment
----------------------------------
1 | Smith | Nice guy!
2 | Wilson | Not so nice.
3 | Lawson | Learns ADO.NET.
4 | Miller | Somebody else.
Here is the code to create this table by your own and print it to the console. To execute the code create a new Console Project, delete all the code in it and copy all the code below into it.
' BEGIN OF CODE ************************************************** ***
Public Class ADODotNETExample
Public Shared Sub main()
' Create a Table
Dim myTable As New System.Data.DataTable
' Create a Column
Dim myColumn As System.Data.DataColumn
' set values for a column
myColumn = New System.Data.DataColumn
myColumn.ColumnName = "ID"
myColumn.DataType = System.Type.GetType("System.Int32")
' add Column to Table
myTable.Columns.Add(myColumn)
myColumn = New System.Data.DataColumn
myColumn.ColumnName = "Name"
myColumn.DataType = System.Type.GetType("System.String")
' add Column to Table
myTable.Columns.Add(myColumn)
myColumn = New System.Data.DataColumn
myColumn.ColumnName = "Description"
myColumn.DataType = System.Type.GetType("System.String")
' add Column to Table
myTable.Columns.Add(myColumn)
' Now you have a empty Table (or to be more exactly
' the definition of a table without any rows)
' Create a DataRow. Remember that you don't instanciate
' a DataRow Object (by using the new() operator)
Dim myDataRow As System.Data.DataRow
' get a DataRow from the Table(description) you just created
myDataRow = myTable.NewRow
' and fill it with Life
myDataRow.Item(0) = 1
myDataRow.Item(1) = "Smith"
myDataRow.Item(2) = "Nice guy!"
' now add the DataRow to the DataTable
myTable.Rows.Add(myDataRow)
' and again for the next row
' you can also address the items by name as the
' item property is overloaded
' get a DataRow from the Table(description) you just created
myDataRow = myTable.NewRow
myDataRow.Item("ID") = 2
myDataRow.Item("Name") = "Wilson"
myDataRow.Item("Description") = "Not so nice."
' now add the DataRow to the DataTable
myTable.Rows.Add(myDataRow)
' and again and again...
' get a DataRow from the Table(description) you just created
myDataRow = myTable.NewRow
myDataRow.Item("ID") = 3
myDataRow.Item("Name") = "Lawson"
myDataRow.Item("Description") = "Learns ADO.NET."
' now add the DataRow to the DataTable
myTable.Rows.Add(myDataRow)
' get a DataRow from the Table(description) you just created
myDataRow = myTable.NewRow
myDataRow.Item("ID") = 4
myDataRow.Item("Name") = "Miller"
myDataRow.Item("Description") = "Somebody else."
' now add the DataRow to the DataTable
myTable.Rows.Add(myDataRow)
Console.WriteLine("Content of myTable")
Console.WriteLine()
Console.WriteLine()
' write content of myTable to console
' first goes the Header
For j As System.Int32 = 0 To myTable.Columns.Count - 1
Console.Write(myTable.Columns(j).ColumnName & ControlChars.Tab)
Next
' new line
Console.WriteLine()
' draw horizontal line
For j As System.Int32 = 0 To 50
Console.Write("-")
Next
Console.WriteLine()
' now print the content of the table
For i As System.Int32 = 0 To myTable.Rows.Count - 1
For j As System.Int32 = 0 To myTable.Columns.Count - 1
Console.Write(myTable.Rows(i).Item(j).ToString & ControlChars.Tab)
Next
Console.WriteLine(ControlChars.Tab & " -> Row : " & i.ToString)
Next
' wait for user to press return
Console.ReadLine()
End Sub
End Class
' END OF CODE ************************************************** *****
Hope this gives you the general idea.
Greetings from Germany.
Daniel Walzenbach
"Roy Lawson" <ro*@xeon.tv> schrieb im Newsbeitrag news:06****************************@phx.gbl...
For what I am doing, there are no constraints on the table
(single table only) so there is only 1 DataTable object in
my DataSet. I set it up this way (1 table w/o relations)
just so I could get it going (crawl before walking).
But, your explanation was very helpful and I think with
that I can figure out programaticly how to proceed. I
suspect I need to focus on the DataColumns collection when
it comes to navigating the DataTable within my DataSet.
My code is on my laptop ... I will submit an update to
this post after I figure it out so that others can learn
to walk with me :-)
Thanks!
-Roy
-----Original Message-----
Roy,
maybe it helps you if you imagine the following:
The DataSet object contains a collection of zero or more
DataTable objects, each of which is an in-memory
representation of a single table. The structure of a
particular DataTable is defined by the DataColumns
collection, which enumerates the columns in a particular
table, and the Constraint collection, which enumerates any
constraints on the table. Together, these two collections
make up the table schema. A DataTable also contains a
DataRows collection, which contains the actual data in the
DataSet.
The DataSet contains a DataRelations collection. A
DataRelation object allows you to create associations
between rows in one table and rows in another table. The
DataRelations collection enumerates a set of DataRelation
objects that define the relationships between tables in
the DataSet. For example, consider a DataSet that contains
two related tables: an Employees table and a Projects
table. In the Employees table, each employee is
represented only once and is identified by a unique
EmployeeID field. In the Projects table, an employee in
charge of a project is identified by the EmployeeID field,
but can appear more than once if that employee is in
charge of multiple projects. This is an example of a one-
to-many relationship; you would use a DataRelation object
to define this relationship.
Excerpt from the book "MCAD/MCSD Training Kit-Developing
Windows-Based Applications with Microsoft Visual
Basic .NET and Microsoft Visual C# ..NET" which I can
truly recommend.
If you for example have a table "myTable" in a
DataSet "myDataSet" and you want to bind the field "ID" of
the first row of the table to a TextBox named TextBox1 do
the following:
TextBox1.Text = myDataSet.Tables("myTable").Rows(0).Item
("ID").ToString
I hope this gives you the general idea. Always visualize
the collections in the ADO.NET model.
Best regards
Daniel Walzenbach
"Roy Lawson" <ro*@xeon.tv> schrieb im Newsbeitrag
news:c4**************************@posting.google.c om... I am having no problems connecting to a DB, creating a DataAdapter, and creating a dataset...and connecting to the data. Using the builtin data objects to do all this.
My only problem now is navigating through the data. I can get the data into a datagrid without any problems, but I want the data to show up in textboxes and use some sort of move next, move previous, move last, etc (like in VB6) command to navigate the data (using buttonX_click). I have been using the learnvisualstudio.net videos and they are great but anyone have a link or tutorial to get me going on this specific task?
(Learning to crawl again)
Roy Lawson
ro*@xeon.tv
