As JBaeske said you need to check whether the attribute exists and use a default if necessary. I wrote some extension methods which help with this.
I have 2 versions of an extension method called GetTypedValue, one returns the default for the type if the attribute doesn't exist and with the other you can supply a default. Be warned that default(string) is null so you would need to use the one with a
supplied default.
Using GetTypedValue in your code would look something like this:
label4.Content = resp.Entity.GetTypedValue("billto_line1", String.Empty); // returns string.empty if billto_line1 not found
If you are using the version with the default value the compiler can infer the type, if not you have to supply it:
label4.Content = resp.Entity.GetTypedValue<string>("billto_line1"); // returns null if billto_line1 not found
The methods also handle AliasedValues automatically (these occur when you used LinkedEntity in your query to do joins).
Here's the code:
public static class EntityExtensions
{
/// <summary>
/// Returns the Id from an entity reference or default(Guid)
/// </summary>
/// <param name="entity">Entity</param>
/// <param name="attributeName">Attribute Name</param>
/// <returns>Guid, either reference Id or default(Guid)</returns>
public static Guid GetEntityReferenceId(this Entity entity, string attributeName)
{
if (entity.Attributes.ContainsKey(attributeName))
{
return GetTypedValue<EntityReference>(entity, attributeName).Id;
}
return default(Guid);
}
/// <summary>
/// Returns the integer from an optionset value or zero if it doesn't exist
/// </summary>
/// <param name="entity">Entity</param>
/// <param name="attributeName">Attribute Name</param>
/// <returns>Integer value</returns>
public static int GetOptionSetValue(this Entity entity, string attributeName)
{
return GetOptionSetValue(entity, attributeName, 0);
}
/// <summary>
/// Returns the integer from an optionset value or the dafaultValue if not found
/// </summary>
/// <param name="entity">Entity</param>
/// <param name="attributeName">Attribute Name</param>
/// <param name="defaultValue">Default optionset value</param>
/// <returns>Integer value</returns>
public static int GetOptionSetValue(this Entity entity, string attributeName, int defaultValue)
{
if (entity.Attributes.ContainsKey(attributeName))
{
return GetTypedValue<OptionSetValue>(entity, attributeName).Value;
}
return defaultValue;
}
/// <summary>
/// Gets a typed value from an entity. If not found the type default is returned
/// </summary>
/// <typeparam name="T">Expected Type</typeparam>
/// <param name="entity">Entity</param>
/// <param name="attributeName">Attribute name</param>
/// <returns>Value or default(T) if not found</returns>
public static T GetTypedValue<T>(this Entity entity, string attributeName)
{
return GetTypedValue(entity, attributeName, default(T));
}
/// <summary>
/// Gets a typed value from an entity
/// </summary>
/// <typeparam name="T">Expected Type</typeparam>
/// <param name="entity">Entity</param>
/// <param name="attributeName">Attribute name</param>
/// <param name="defaultValue">Default value if not found</param>
/// <returns>Value or default if not found</returns>
public static T GetTypedValue<T>(this Entity entity, string attributeName, T defaultValue)
{
if (entity.Attributes.ContainsKey(attributeName))
{
return ReturnAttributeValue<T>(entity[attributeName]);
}
return defaultValue;
}
private static T ReturnAttributeValue<T>(object attributeValue)
{
AliasedValue aliasedValue = attributeValue as AliasedValue;
if (aliasedValue != null)
{
return (T)(aliasedValue).Value;
}
return (T) attributeValue;
}
}
