Interacting with Databases Using ASP.NET 2.0 with the Microsoft Data Access Application Block - Retrieving a single value using the Data Access Application Block

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In this section, we shall retrieve a single value onto the form by passing a SELECT statement to the Data Access Application Block. 

The following is the complete code:

ImportsSystem.Data
ImportsMicrosoft.Practices.EnterpriseLibrary.Data.Sql
ImportsMicrosoft.Practices.EnterpriseLibrary.Data
PartialClass _Default
    Inherits System.Web.UI.Page
    Protected Sub btnConnect_Click(ByVal sender As Object, ByVal
e As System.EventArgs) Handles btnConnect.Click
        Me.lblMsg.Text = getSingleValue("select count(*) from
HumanResources.department")
    End Sub
    Private Function getSingleValue(ByVal SQl As String) As
String
        Dim db As SqlDatabase = DirectCast
(DatabaseFactory.CreateDatabase("AdventureWorks"), SqlDatabase)
        Dim dt As DataTable = db.ExecuteDataSet(CommandType.Text,
SQl).Tables(0)
        Return dt.Rows(0)(0) & ""
    End Function
EndClass

In the above code, there is nothing much to explain. Up to now, I didn’t implement exception handling in any of the above code. Just to help you understand, we can even handle errors efficiently by rewriting the above program as follows:

ImportsSystem.Data
ImportsMicrosoft.Practices.EnterpriseLibrary.Data.Sql
ImportsMicrosoft.Practices.EnterpriseLibrary.Data
PartialClass _Default
    Inherits System.Web.UI.Page
    Protected Sub btnConnect_Click(ByVal sender As Object, ByVal
e As System.EventArgs) Handles btnConnect.Click
        Try
            Me.lblMsg.Text = getSingleValue("select count(*) from
HumanResources.department")
        Catch ex As Exception
            Me.lblMsg.Text = ex.Message
        End Try
    End Sub
    Private Function getSingleValue(ByVal SQl As String) As String
        Try
            Dim db As SqlDatabase = DirectCast
(DatabaseFactory.CreateDatabase("AdventureWorks"), SqlDatabase)
            Dim dt As DataTable = db.ExecuteDataSet
(CommandType.Text, SQl).Tables(0)
            Return dt.Rows(0)(0) & ""
        Catch ex As Exception
            Throw New Exception("Unable to retrieve value:" &
ex.Message)
        End Try
    End Function
EndClass

Next: Executing a DML statement using the Data Access Application Block >>
 

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