Question

In the linq to xml query below, I have 2 properties that are a list<string>, DefaultValues and Values.

If either of these elements are empty, I would like to set that property of the LiteValueParameter object to a new, empty list:

Values = new List<string>();

Instead, the linq query is giving me something lke this:

Values = new List<string>();
Values.Add("");

Is there any way to prevent an empty item being added to the list if I have an empty element in my XML?

Linq code:

//linq query
List<LiteValueParameter> valParams = new List<LiteValueParameter>();
valParams = (from c in doc.Descendants("Parameters").Descendants("Parameter")
             where (LiteParameterType)Enum.Parse(typeof(LiteParameterType), c.Element("ParameterType").Value, true) == LiteParameterType.Value
             select new LiteValueParameter()
             {
                 Id = c.Attribute("Id").Value,
                 DataType = Type.GetType(c.Element("DataType").Value, true),
                 DefaultValues = c.Elements("DefaultValues").Select(element => element.Value).ToList(),
                 DisplayText = c.Element("DisplayText").Value,
                 IsRequired = Convert.ToBoolean(c.Element("IsRequired").Value),
                 MinCount = Convert.ToInt32(c.Element("MinCount").Value),
                 MaxCount = Convert.ToInt32(c.Element("MaxCount").Value),
                 MinValue = c.Element("MinValue").Value,
                 MaxValue = c.Element("MaxValue").Value,
                 ParameterName = c.Element("ParameterName").Value,
                 Values = c.Elements("Values").Select(element => element.Value).ToList(),
                 ParameterType = (LiteParameterType)Enum.Parse(typeof(LiteParameterType), c.Element("ParameterType").Value, true),
                 DisplayType = c.Element("DisplayType").Value
             }).ToList();

XML Code:

<Parameters>
  <Parameter Id="PermissionList">
    <ParameterType>Value</ParameterType>
    <ParameterName>Permissions</ParameterName>
    <DisplayType>ListBox</DisplayType>
    <DisplayText>Permissions</DisplayText>
    <IsRequired>true</IsRequired>
    <MinValue />
    <MaxValue />
    <DefaultValues />
    <Values />
    <DataType>System.String</DataType>
    <MinCount>1</MinCount>
    <MaxCount>1</MaxCount>
  </Parameter>
</Parameters>

Answer 1

I suppose you could work around it like this:

DefaultValues = (c.Elements("DefaultValues").Count() == 1 && c.Elements("DefaultValues").First().Value == string.Empty) ? new List<string>() : 
c.Elements("DefaultValues").Select(element => element.Value).ToList(),

This approach feels very “hacky” though. Instead I would change your XML to have a DefaultValue element that you query instead:

<DefaultValues>
  <DefaultValue>Foo</DefaultValue>
</DefaultValues>

This is much more natural and now you can just write your query like

DefaultValues = c.Descendants("DefaultValue").Select(element => element.Value).ToList(),

This will return an empty collection if you just have

<DefaultValues/>