What to do about NullReferenceException?

if you perform a loop for all your items and test for null - you can set them to string.empty if they are null, then when populating your textboxes it will not bomb on yu

you could write a routine to convert to NonNullableString like this:

private string ToNonNullableString(object value)
{
    string result = string.empty;
    if (value != null)
    {
        result = value.ToString();
    }
    return result;
}
 
// Then call it like this:
txtPostalName.Text = ToNonNullableString(nodeCorAdd.Attributes.GetNamedItem("postalname").Value);

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Actually, I think your example check is checking the value of the item for null, but if the attribute doesn't exist, won't THAT check fail because the object reference is NULL, thereby preventing checking its value. I assume that's how GetNamedItem works ... by returning a null if it's not found.

Anyway, why not create a small wrapper function that does both checks. Then you just call the wrapper, once for each field.

Off the top of my head, I don't know the Class names returned by these, so I'll use "var" as a placeholder...

MyWrapperToSetFieldValue(txtPostalName, "postalname");

private void MyWrapperToSetFieldValue(Control ctl, string fieldName)
{
    var node = nodeCorAdd.Attributes.GetNamedItem(fieldName);
    if (var != null && var.Value != null)
    {
        ctl.Text = var.Value;
    }
    else {
       ctl.Text = string.empty; // can also use TextBox as the type, if they're all text boxes. and make wrapper classes for each type (overloading) or determnine type of control in here.
    }
}

Well, which part is returning null--GetNamedItem, or the Value property of the returned item? Also, to clean up your code, you can use the "Coalesce" operator, written as "??". It works like this:

System.String someString = stringValuePossiblyNull ?? "Fallback if the value to the left is null";

The compiler, in this case, will check the value of "stringValuePossiblyNull"; if it is null, it will assign the vaule to the right of the coalesce operator. If it is not null, it will assign the value as usual.

Another option is to use an XML schema in which you require certain attributes. There are quite a few ways of going about your problem, but really, I hate to say it, but you're being lazy here. There's no reason you can't check for something as necessary as this--not everything can be just seamlessly built in and magically done FOR you.

Anyways, a more specific solution is provided in the following code snippet. If my thoughts are correct, it will still throw a NullReferenceException because I think you're checking the wrong value for "null", but we'll see :)

Hope it helps,
Nate

txtPostalName.Text = nodeCorAdd.Attributes.GetNamedItem("postalname").Value ?? System.String.Empty;
 
// If this doesn't work, and you're worried about too many lines, of code, you could use the following,
// assuming the returned item is null (which I'm thinking it is)
 
txtPostalName.Text = (nodeCorAdd.Attributes.GetNamedItem("postalname") != null) ?nodeCorAdd.Attributes.GetNamedItem("postalname").Value ?? System.String.Empty : System.String.Empty;
 
// This performs a check for both fields that may be null.

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