Insert and Update with XML in stored procedure - asp.net

Question

I need some help in using a stored procedure in my case below: I have a table with a single XML column which takes in fields VoucherCode and Quantity, the data in SQL xml column looks like this:
<CampaignVoucher xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" VoucherCode="Vouch001" Quantity="2" />
The below method will call my stored procedure to check if a particular voucher exist based on my voucher code and then either add a new row or update an existing voucher in my gridview:
Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnAdd.Click
Dim dbCommand As DbCommand = Nothing
'Dim cmd As New SqlCommand()
If TextBox1.Text = "" Or DropDownList1.SelectedIndex = 0 Then
Exit Sub
End If
Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("Test").ConnectionString)
Dim da As New SqlDataAdapter("SELECT CustomerID, VoucherXML FROM Customers", con)
Dim cmd As New SqlCommand("Campaign_InsertRewardsVoucher_XML", con)
cmd.CommandType = CommandType.StoredProcedure
Dim dt As New DataTable()
da.Fill(dt)
' Here we'll add a blank row to the returned DataTable
Dim dr As DataRow = dt.NewRow()
dt.Rows.InsertAt(dr, 0)
'Creating the first row of GridView to be Editable
GridView1.EditIndex = 0
GridView1.DataSource = dt
GridView1.DataBind()
'Changing the Text for Inserting a New Record
DirectCast(GridView1.Rows(0).Cells(0).Controls(0), LinkButton).Text = "Insert"
' Serialization ----------------------------
Dim cm As New CampaignVoucher(DropDownList1.SelectedValue, TextBox1.Text)
Dim serializer As New XMLserializer(cm.[GetType]())
Dim memoryStream As New MemoryStream()
Dim writer As New XmlTextWriter(memoryStream, Encoding.UTF8)
serializer.Serialize(writer, cm)
'get the stream from the writer
memoryStream = TryCast(writer.BaseStream, MemoryStream)
'apply encoding to the stream
Dim enc As New UTF8Encoding()
Dim xml As String = enc.GetString(memoryStream.ToArray()).Trim()
' -------------------------------------------
cmd.Parameters.Add("#p1", SqlDbType.VarChar, 50).Value = DropDownList1.SelectedValue
cmd.Parameters.Add("#p2", SqlDbType.Text).Value = xml
cmd.Connection = con
con.Open()
cmd.ExecuteScalar()
con.Close()
GridView1.EditIndex = -1
BindData()
TextBox1.Text = ""
End Sub
Backtrack a little, I wrote this working stored proc as shown below for the same purpose just that it was meant for a conventional storage: 1 table with a VoucherCode and Quantity column, now with the XML column, now encapsulating both VoucherCode and Quantity values, I am lost to how to rewrite my stored proc, tried different ways but apparently I made a mess out of it, please advice, thanks!:
ALTER PROCEDURE [dbo].[Campaign_InsertRewardsVoucher]
#VoucherCode nvarchar(50) =NULL,
#Quantity int = NULL
--#ExistingQuantity int = NULL
AS
BEGIN
DECLARE #ExistingQuantity Int = Null
IF EXISTS (SELECT * FROM ForTest_Campaign_Voucher WHERE VoucherCode=#VoucherCode)
BEGIN
SET #ExistingQuantity = (SELECT Quantity from ForTest_Campaign_Voucher Where VoucherCode=#VoucherCode)
SET #ExistingQuantity = (#ExistingQuantity + #Quantity)
UPDATE ForTest_Campaign_Voucher SET VoucherCode=#VoucherCode, Quantity=#ExistingQuantity Where VoucherCode=#VoucherCode
END
ELSE
INSERT INTO ForTest_Campaign_Voucher(VoucherCode, Quantity) VALUES(#VoucherCode, #Quantity)
END

Answer 1

ALTER PROCEDURE [dbo].[Campaign_InsertRewardsVoucher]
#VoucherCode nvarchar(50) =NULL,
#Quantity int = NULL
AS
BEGIN
DECLARE #ExistingQuantity Int
SET #ExistingQuantity = (SELECT xmlFieldName.value('(/CampaignVoucher/#Quantity)[1]', 'int')
FROM ForTest_Campaign_Voucher
WHERE xmlFieldName.value('(/CampaignVoucher/#VoucherCode)[1]', 'nvarchar(50)') = #VoucherCode)
IF #ExistingQuantity IS NULL
BEGIN
INSERT INTO ForTest_Campaign_Voucher
(
xmlFieldName
)
VALUES
(
'<CampaignVoucher xmlns:xsd="http://www.w3.org/2001/XMLSchema" VoucherCode="' + #VoucherCode + '" Quantity="' + CAST(#Quantity AS NVARCHAR(16)) + '" />'
)
END
ELSE
DECLARE #NewQuantity INT
SET #NewQuantity = #ExistingQuantity + #Quantity
UPDATE ForTest_Campaign_Voucher
SET xmlFieldName='<CampaignVoucher xmlns:xsd="http://www.w3.org/2001/XMLSchema" VoucherCode="' + #VoucherCode + '" Quantity="' + CAST(#NewQuantity AS NVARCHAR(16)) + '" />'
WHERE xmlFieldName.value('(/CampaignVoucher/#VoucherCode)[1]', 'nvarchar(50)') = #VoucherCode
END
GO