Process Data With in XML File

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Introduction

This Article Illustrate how to process data within XML File. For this Article I have developed a small Application that allows users to:

�         Read Data from XML file and display it in the ASP.NET DataGrid Control.

�         Write Data in XML File.

�         Updating Data in XML File.

Getting Started

There are 2 main files:

1.     Products.xml

2.     ItemXML.vb 

XML file (Products.xml) contains three elements

1. ItemID � functioning as a primary key
2. ProductName
3. Price

<SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"><o:p></o:p> <?xml version="1.0" standalone="yes"?>
<Items>

<Item>
    <ItemID>1</ItemID>
    <ProductName>8-23 hours </ProductName>
    <Price>99</Price>
  </Item>
  <Item>
    <ItemID>2</ItemID>
    <ProductName>1 day</ProductName>
    <Price>92</Price>
  </Item>
</Items>

ItemXML.vb contains all the business logic that I have used to process XML File

1. GetAll ( Return All the Items from XML File)
2. Insert
3. Update
4. GetByID (Its Takes ItemID return the requested item detail from XML File)

Reading Data from XML file and Binding it with DataGrid

I have used DataSet Object�s ReadXML method to Read data from XML file and then bind it to DataGrid control.

Public Function GetAll(ByVal Path As String) As DataTable
            Dim dt As New DataTable
            Dim ds As New DataSet
            ds.ReadXml(Path & "/Products.xml")
            Dim dt_ret As DataTable = ds.Tables(0) 
            Return dt_ret

        End Function
Dim ObjXMLData as New BusinessLayer.ItemXML
            dt = ObjXMLData.GetAll(Server.MapPath("/").ToString())
            DataGrid1.DataSource = dt
            DataGrid1.DataBind()

Variable �Path� contains Server.MapPath(�/�) .. The Server.MapPath is not Accessible from the Class file, that is why I have sent it from the code behind file.

Inserting Data in XML File

 Public Function Insert(ByVal ProductName As String, ByVal Price As Long, ByVal Path As String) As Long
            Try
                Dim dr As DataRow
                Dim ds As New DataSet
                ds.ReadXml(Path & "/Products.xml")

                dr = ds.Tables(0).NewRow
                dr("ItemID") = CType(ds.Tables(0).Rows(ds.Tables(0).Rows.Count - 1)("ItemID"), Long) + 1
                dr("ProductName") = ProductName
                dr("Price") = Price
                ds.Tables(0).Rows.Add(dr)
                ds.WriteXml(Path & "/Products.xml", XmlWriteMode.WriteSchema)
                Return 1
            Catch ex As Exception
                Return 0
            End Try
        End Function

Insert function takes 3 parameters (ProductName, Price, Path).

Item ID will be generated automatically by incrementing the last item ID in XML file by using the code:

dr("ItemID") = CType(ds.Tables(0).Rows(ds.Tables(0).Rows.Count - 1)("ItemID"), Long) + 1

ds.Tables(0).Rows.Count -1 gives the last index value of the DataSet object

For Writing to the XML File, I am using WriteXml method of the DataSet that takes the path of the file as a Parameter.

Note: set permissions on the directory, if you do NOT want to make ALL files writeable, you could probably get away with setting the permissions on the Products.xml file itself.

Updating Data in XML File

 Public Function Update(ByVal Item_ID As Long, ByVal ProductName As String, ByVal Price As Long, ByVal Path As String) As Long
            Try
                Dim ds As New DataSet
                ds.ReadXml(Path & "/Products.xml")
                Dim dr As DataRow
                dr = ds.Tables(0).NewRow
                Dim a As Integer
                Dim b As Integer
                For b = 0 To ds.Tables(0).Rows.Count - 1
                    If Item_ID = ds.Tables(0).Rows(b)("ItemID") Then

                        ds.Tables(0).Rows(b)("ItemID") = Item_ID
                        ds.Tables(0).Rows(b)("ProductName") = ProductName
                        ds.Tables(0).Rows(b)("Price") = Price
                        ds.WriteXml(Path & "/Products.xml", XmlWriteMode.WriteSchema)

                    End If
                Next
                Return 1
            Catch ex As Exception
                Return 0
            End Try

        End Function