如果我理解得很好 - 这是WF Designer错误。当我不得不InArgument<T>在我的自定义 WF 设计器中支持默认值定义时，我遇到了这个问题。我仍然对缺乏对这个基本程序的支持感到惊讶。
失败的原因有2个：
{x:Null}inx:Class属性的定义xmlns:this属性定义无效- 主要问题是 Argument 的默认值定义无效：this:_effe.MyArgument="asd"。参数默认值的定义应等于：MyXamlClassName.MyArgument="asd"。例如，如果您的 x:Cass 定义为 x:Class="MyNamespace.MyClass"，则参数定义应为：MyClass.MyArgument="asd"。
我通过干预 XAML 保存过程来解决它：调用后
_workflowDesigner.Save(_editedFile);
我添加了这两行：
#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);
});
}
常量定义为：
#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
该解决方案也应该可以解决您的问题。