If I understand well - this is WF Designer bug.
I've faced with this problem when I had had to support default value definition for InArgument<T> in my custom WF designer. I still surprised lack of support for this basic procedure.
There are 2 reason of failure:
- Definition of
{x:Null} in x:Class attribute
- Invalid definition of
xmlns:this attribute
- And the main problem is invalid definition of Argument's default value: this:_effe.MyArgument="asd". The definition of default value for argument should be equal to this:MyXamlClassName.MyArgument="asd". For example, if your x:Cass definition is x:Class="MyNamespace.MyClass", Argument definition should be this:MyClass.MyArgument="asd".
I resolved it by intervention into XAML saving process:
After calling of
_workflowDesigner.Save(_editedFile);
I added these two lines:
#region x:Class and Argument<T> default value issues solution
await CreateAttributeValue(_editedFile, ConstXClassAttributeName, typeof(App).Namespace + "." + Path.GetFileNameWithoutExtension(_editedFile));
//should finish first operation before second operation begins to avoid I/O exception
await CreateAttributeValue(_editedFile, ConstNamespaceAttributeName, ConstXamlClrNamespace + typeof(App).Namespace);
await RepairArgsAttributes(_editedFile);
#endregion
This is the methods definition:
/// <summary>
/// Reason of using of this method: bug in workflow designer. When you save your xaml file, WF Designer assign "{x:Null}" to x:Class attribute
/// Bug: In addition, if you want to set default value for your InArgument<T>, it defines attribute "this" (namespace declaration) with empty value. When you try to open your file, designer fails to parse XAML.
/// </summary>
/// <param name="editedFile"></param>
/// <param name="attribteName"></param>
/// <param name="attributeValueToReplace"></param>
private static async Task CreateAttributeValue(string editedFile, string attribteName, string attributeValueToReplace)
{
XmlDocument xmlDoc = new XmlDocument();
await Task.Run(() => xmlDoc.Load(editedFile));
await Task.Run(() =>
{
var attributteToReplace = xmlDoc.FirstChild.Attributes?[attribteName];
if (null != attributteToReplace)
{
xmlDoc.FirstChild.Attributes[attribteName].Value = attributeValueToReplace;
xmlDoc.Save(editedFile);
}
});
}
/// <summary>
/// Bug in Workflow designer: workflow designer saves declaration for In/Out Arguments in invalid format. Means, that it is unable to open the same file it saved itself. This method fixes the Arguments declaration in XAML xmlns
/// </summary>
/// <param name="editedFile"></param>
/// <returns></returns>
private async Task RepairArgsAttributes(string editedFile)
{
XmlDocument xmlDoc = new XmlDocument();
await Task.Run(() => xmlDoc.Load(editedFile));
await Task.Run(() =>
{
for (int i = 0; i < xmlDoc.FirstChild.Attributes.Count; i++)
{
if (xmlDoc.FirstChild.Attributes[i].Name.StartsWith(ConstInvalidArgStarts))
{
string innvalidAttrName = xmlDoc.FirstChild.Attributes[i].Name;//extraction of full argument declaration in xmlns
string[] oldStrings = innvalidAttrName.Split('.');//extraction of arguemnt name string
string localName = Path.GetFileNameWithoutExtension(editedFile) + "." + oldStrings[1];//build valid argment declaration without perfix
string valueBackup = xmlDoc.FirstChild.Attributes[i].Value;//saving of default value of Arguemnt<T>
xmlDoc.FirstChild.Attributes.RemoveNamedItem(xmlDoc.FirstChild.Attributes[i].Name);//removal of invalid Arguemnt declaration with default value. WARNING: when you remove attribue, at this moment you have another item at the place xmlDoc.FirstChild.Attributes[i]
//definition of new valid attribute requries: set separelly attribute prefix, localName (not "name" - it causes invalid attribute definition) and valid namespace url (in our case it's namespace deifinition in "this")
XmlAttribute attr = xmlDoc.CreateAttribute(ConstArgPrefix, localName, xmlDoc.FirstChild.Attributes[ConstNamespaceAttributeName].Value);
attr.Value = valueBackup;
xmlDoc.FirstChild.Attributes.InsertBefore(attr, xmlDoc.FirstChild.Attributes[i]);//define new correct Argument declaration attribute at the same place where was invalid attribute. When you put valid attribute at the same place your recover valid order of attributes that was changed while removal of invalid attribute declaration
}
}
xmlDoc.Save(editedFile);
});
}
The constants definition are:
#region Constants
private const string ConstXClassAttributeName = "x:Class";
private const string ConstXamlClrNamespace = "clr-namespace:";
private const string ConstNamespaceAttributeName = "xmlns:this";
private const string ConstInvalidArgStarts = @"this:_";
private const string ConstArgPrefix = @"this";
#endregion
This solution should resolve your issue too.
