In this article, I will explain how to use XDocument to read XML Attribute value.

Step 1: Add a TextBox and Button, TextBox will be used to search the attribute value based on the Id entered in the textbox.

<asp:TextBox ID="txtId" runat="server"></asp:TextBox>
<asp:Button ID="btnGetValue" Text="Get Value" runat="server" OnClick="btnGetValue_Click" />

Step 2: Create a XML file like below structure.

<Messages>
        <Message id='One'>
                <Display>Messageid is one.</Display>
        </Message>
        <Message id='Two'>
                <Display>Messageid is two.</Display>
        </Message>
        <Message id='Three'>
                <Display>Messageid is three.</Display>
        </Message>
        <Message id='Four'>
                <Display>Messageid is four.</Display>
        </Message>
        <Message id='Four'>
                <Display>Messageid is again four.</Display>
        </Message>
        <Message id='One'>
                <Display>Messageid is again one.</Display>
        </Message>
</Messages>
 

Step 3: Create a method GetValues which will return List of matching elements found in the XML document.

public static List<string> GetValues(string strFileName, string strDescendants, string strAttribute, string strAttributeValue, string strElement)
{
        XDocument xmlDoc = XDocument.Load(strFileName); //Open XML file
        var xmlValue = from c in xmlDoc.Descendants(strDescendants)
                                where c.Attribute(strAttribute).Value.ToLower().Equals(strAttributeValue.ToLower())
                                select (string)c.Element(strElement);
        List<string> strList = xmlValue.ToList<string>();
        return strList;
}

Step 4: btnGetValue_Click event of button will invoke GetValues
 

protected void btnGetValue_Click(object sender, EventArgs e)
{
        string strFileName = Server.MapPath("Message.xml");
        string strDescendants = "Message"; 
        string strAttribute = "id";
        string strAttributeValue = txtId.Text;
        string strElement = "Display";
        List<string> lstValues = GetValues(strFileName, strDescendants, strAttribute, strAttributeValue, strElement);
        if (lstValues.Count > 0)
        {
                foreach (string strValue in lstValues)
                {
                        Response.Write(strValue + "<br/>");
                }
        }
        else
        {
                Response.Write("No matching record found.");
        }
}