language for databases

[Scott Baxter]

Hello,

In the new vb.net is a thing called dataset, which I guess is a standalone
database you can create and play with.

The following code works fine for that.

But I can't seem to define things so that it would work against a real
database.

Here's code that creates an access database, with no structure or fields on
the disk:


If CreateAccessDatabase("e:\test2.mdb") = True Then
MsgBox("Database Created")
Else
MsgBox("Database Creation Failed")
End If

Public Function CreateAccessDatabase( _
ByVal DatabaseFullPath As String) As Boolean
Dim bAns As Boolean
Dim cat As New ADOX.Catalog()
Try


'Make sure the folder
'provided in the path exists. If file name w/o path
'is specified, the database will be created in your
'application folder.

Dim sCreateString As String
sCreateString = _
"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & _
DatabaseFullPath
cat.Create(sCreateString)

bAns = True

Catch Excep As System.Runtime.InteropServices.COMException
bAns = False
'do whatever else you need to do here, log,
'msgbox etc.
Finally
cat = Nothing
End Try
Return bAns
End Function


I want to use code like the code below to add the fields to the database.

Is there a way to do this?

Thanks.

Scott




Public Sub createdataset()
'Dim ds As New DataSet()
' Create a table; set its initial capacity.
Dim dtEmp As New DataTable("Employees")
dtEmp.MinimumCapacity = 200
' Create all columns.
' You can create a DataColumn and then add it to the Columns
collection.
Dim dcFName As New DataColumn("FirstName", GetType(String))
dtEmp.Columns.Add(dcFName)
' Or you can create an implicit DataColumn with the Columns.Add
method.
dtEmp.Columns.Add("LastName", GetType(String))
dtEmp.Columns.Add("BirthDate", GetType(Date))
' When you have to set additional properties, you can use an
explicit
' DataColumn object, or you can use a With block.
With dtEmp.Columns.Add("HomeAddress", GetType(String))
.MaxLength = 100
End With
' (When you must set only one property, you can be more concise,
' even though the result isn't very readable.)
dtEmp.Columns.Add("City", GetType(String)).MaxLength = 20
' Create a calculated column by setting the Expression
' property or passing it as the third argument to the Add method.
dtEmp.Columns.Add("CompleteName", GetType(String), _
"FirstName + ' ' + LastName")
' Create an identity, auto-incremented column.
Dim dcEmpId As New DataColumn("EmpId", GetType(Integer))
dcEmpId.AutoIncrement = True ' Make it auto-increment.
dcEmpId.AutoIncrementSeed = 1
dcEmpId.AllowDBNull = False ' Default is True.
dcEmpId.Unique = True ' All key columns should be unique.
dtEmp.Columns.Add(dcEmpId) ' Add to Columns collection.
' Make it the primary key. (Create the array on-the-fly.)
dtEmp.PrimaryKey = New DataColumn() {dcEmpId}
' This is a foreign key, but we haven't created the other table yet.
dtEmp.Columns.Add("DeptId", GetType(Integer))
' Add the DataTable to the DataSet.
ds.Tables.Add(dtEmp)
End Subl

 

[PvdG42]

Hello,

In the new vb.net is a thing called dataset, which I guess is a standalone
database you can create and play with.

The following code works fine for that.

But I can't seem to define things so that it would work against a real
database.

Here's code that creates an access database, with no structure or fields
on
the disk:

<snip>

You need to learn about datasets and what they actually are, as your
statement above "In the new vb.net is a thing called dataset, which I guess
is a standalone database you can create and play with." indicates that you
need to study.

A dataset is an in-memory repository of data retrieved from one or more data
sources for manipulation by your application. The data source in question
may be a relational database table(s) data stored in the tables collection
in your dataset. Datasets support the ADO.NET disconnected model for data
applications where data is retrieved from data source(s) and placed in the
dataset for application use with the connection to the original data source
active only long enough to retrieve the data. The application works with
data in the tables in the dataset and, if updates need to be made permanent,
the connection to the original data source is reestablished only long enough
to send the updates from the dataset back to the data source.

There are numerous articles and examples available on MSDN
(msdn.microsoft.com) to help you get comfortable with ADO.NET.

http://blogs.msdn.com/bethmassi/archive/2008/03/18/new-video-tutorials-from-the-community.aspx

http://social.msdn.microsoft.com/fo.../thread/3be9ec05-d9d7-4c7c-a131-d2a4d9b24dec/

 

[Cor Ligthert[MVP]]

Scott,

I missed your question, we have a fine sample for your question on our
website.

It is almost like your code by the way.
http://www.vb-tips.com/CreateMDB.aspx

However, it is not used almost anymore, I would simply download a SQL Server
Express 2008 in your case as that is freeware

Cor

 

[Cor Ligthert[MVP]]

Scott,

I missed your question, we have a fine sample for your question on our
website.

It is almost like your code by the way.
http://www.vb-tips.com/CreateMDB.aspx

However, it is not used almost anymore, I would simply download a SQL Server
Express 2008 in your case as that is freeware

Cor