I am parsing an XML file in C#, how I can make sure the code is not breaking if XML does not have one of these fields I am parsing? I don't want to through an exception as well.

       StringBuilder output = new StringBuilder();

        var xDocument = XDocument.Load(filePath);
        string xml = xDocument.ToString();
        XDocument doc = XDocument.Parse(xml);
        var col = doc.Root.Elements("LineItems")
                     .Elements("LineItem")
                     .Elements("OrderLine")
                     .Select(e => new
                     {
                         PurchaseOrderNumber = doc.Root.Element("Header").Element("OrderHeader").Element("Purchase").Value,
                         InternalOrderNumber = doc.Root.Element("Header").Element("OrderHeader").Element("InternalOrderNumber").Value,
                         VendorPartNumber = e.Element("VendorPartNumber").Value,
                         ItemStatus = e.Element("ItemStatus").Value,
                         Date = e.Element("ExpectedDate").Value
                     });

For example, I removed ExpectedDate from XML and this is breaking. what can I add to this code that is not breaking when XML fields do not exist?

I added this and it works: ate = e.Element("ExpectedDate")?.Value,

But now if ExpectedDate is not existed this would be 1/1/0001 12:00:00 AM - How I can have an empty string so this line won't break:

  OrderLine orderline = new OrderLine() { ItemStatus = item.ItemStatus, VendorPartNumber = item.VendorPartNumber, Date = Convert.ToDateTime(item.Date) };

This is XML sample:

<Purchase>
    <Header>
    <OrderHeader>
        <TradingId>OPIE</TradingId>
    </OrderHeader>
</Header>
<LineItems>
    <LineItem>
        <OrderLine>
            <UnitPrice>1073.25</UnitPrice>
            <ExtendedLineAmount>1073.25</ExtendedLineAmount>
            <ItemStatus>Backorder</ItemStatus>
            <ExpectedDate>2022-05-25</ExpectedDate>
        </OrderLine>
    </LineItem>
    <LineItem>
        <OrderLine>
            <UnitPrice>292.410000</UnitPrice>
            <ExtendedLineAmount>584.82</ExtendedLineAmount>
            <ItemStatus>Released</ItemStatus>
            <ExpectedDate>2022-06-29</ExpectedDate>
        </OrderLine>
    </LineItem>

</LineItems>

CodePudding user response：

Please try the following solution.

I saved your XML as a "e:\temp\alma.xml" file. And intentionally commented out

<!--<ExpectedDate>2022-06-29</ExpectedDate>-->

A question mark is standard way in the .Net Framework way to handle missing values as nulls:

ExpectedDate = e.Element("ExpectedDate")?.Value

Commented out ?? "default value" should match an expected data type.

XML

<?xml version="1.0"?>
<Purchase>
    <Header>
        <OrderHeader>
            <TradingId>OPIE</TradingId>
        </OrderHeader>
    </Header>
    <LineItems>
        <LineItem>
            <OrderLine>
                <UnitPrice>1073.25</UnitPrice>
                <ExtendedLineAmount>1073.25</ExtendedLineAmount>
                <ItemStatus>Backorder</ItemStatus>
                <ExpectedDate>2022-05-25</ExpectedDate>
            </OrderLine>
        </LineItem>
        <LineItem>
            <OrderLine>
                <UnitPrice>292.410000</UnitPrice>
                <ExtendedLineAmount>584.82</ExtendedLineAmount>
                <ItemStatus>Released</ItemStatus>
                <!--<ExpectedDate>2022-06-29</ExpectedDate>-->
            </OrderLine>
        </LineItem>
    </LineItems>
</Purchase>

c#

void Main()
{
    const string filePath = @"e:\temp\alma.xml";
    
    XDocument doc = XDocument.Load(filePath);
    var col = doc.Descendants("OrderLine")
            .Select(e => new
            {
                UnitPrice = e.Element("UnitPrice").Value,
                ExtendedLineAmount = e.Element("ExtendedLineAmount").Value,
                ItemStatus = e.Element("ItemStatus").Value,
                ExpectedDate = e.Element("ExpectedDate")?.Value // ?? "default Value"
            });
    Console.WriteLine(col);
}

Output

 ------------ -------------------- ------------ -------------- 
| UnitPrice  | ExtendedLineAmount | ItemStatus | ExpectedDate |
 ------------ -------------------- ------------ -------------- 
|    1073.25 |            1073.25 | Backorder  | 2022-05-25   |
| 292.410000 |             584.82 | Released   | null         |
 ------------ -------------------- ------------ -------------- 

CodePudding user response：

What works for me is to make an extension for XElement that returns true if the element exists (and then supply a default value if it doesn't):

public static class Extensions
{
    public static bool TryGetElement(
        this XElement pxel, 
        string name, 
        out XElement xel)
    {
        xel = pxel.Element(name);
        return xel != null;
    }
}

Using it like this:

var doc = XDocument.Parse(source);
var col = doc.Root.Elements("LineItems")
    .Elements("LineItem")
    .Elements("OrderLine")
    .Select(e => new
    {
        PurchaseOrderNumber = doc.Root.Element("Header").Element("OrderHeader").Element("Purchase").Value,
        VendorPartNumber = e.Element("VendorPartNumber").Value,
        ItemStatus = e.Element("ItemStatus").Value,
        Date = e.TryGetElement("ExpectedDate", out XElement xel) ? 
            xel.Value : 
            String.Empty
    });

foreach (var orderline in col)
{
    Console.WriteLine(orderline.ToString());
}

TESTING

Where test source XML (made pathological by removing the 2nd ExpectedDate) is:

const string source =
@"<Purchase>
    <Header>
        <OrderHeader>
            <Purchase>12345</Purchase>
        </OrderHeader>
    </Header>
    <LineItems>
        <LineItem>
            <OrderLine>
                <VendorPartNumber>1</VendorPartNumber>
                <UnitPrice>1073.25</UnitPrice>
                <ExtendedLineAmount>1073.25</ExtendedLineAmount>
                <ItemStatus>Backorder</ItemStatus>
                <ExpectedDate>2022-05-25</ExpectedDate>
            </OrderLine>
        </LineItem>
        <LineItem>
            <OrderLine>
                <VendorPartNumber>2</VendorPartNumber>
                <UnitPrice>292.410000</UnitPrice>
                <ExtendedLineAmount>584.82</ExtendedLineAmount>
                <ItemStatus>Released</ItemStatus>
            </OrderLine>
        </LineItem>
    </LineItems>
</Purchase>";