Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>If your 'predicate' is a well-known string and don't need to be an expression evaluated at runtime you surely can do something like this, throwing away the <em>InArgument</em> and avoid the constructor:</p> <pre><code>public class Eval&lt;T, TResult&gt; : Activity&lt;TResult&gt; { public string Expression { get; set; } [RequiredArgument] public InArgument&lt;T&gt; Value { get; set; } protected override Func&lt;Activity&gt; Implementation { get { if (string.IsNullOrEmpty(Expression)) { return base.Implementation; } return () =&gt; new Assign&lt;TResult&gt; { Value = new InArgument&lt;TResult&gt;(new VisualBasicValue&lt;TResult&gt;(Expression)), To = new ArgumentReference&lt;TResult&gt;("Result") }; } set { throw new NotSupportedException(); } } } </code></pre> <p>and call it this way:</p> <pre><code>var activity = new Eval&lt;int, int&gt;() { Expression = "Value + 2" }; var inputArgs = new Dictionary&lt;string, object&gt;() { { "Value", 5 } }; Console.WriteLine("RESULT: " + WorkflowInvoker.Invoke&lt;int&gt;(activity, inputArgs)); </code></pre> <hr/> <p><strong>EDIT</strong>: check that even with <code>Predicate.ExpressionText</code> not commented, it has no effect whatsoever:</p> <pre><code>public class NativeEval&lt;T, TResult&gt; : NativeActivity&lt;TResult&gt; { [RequiredArgument] public InArgument&lt;string&gt; ExpressionText { get; set; } [RequiredArgument] public InArgument&lt;T&gt; Value { get; set; } private Assign Assign { get; set; } private VisualBasicValue&lt;TResult&gt; Predicate { get; set; } private Variable&lt;TResult&gt; ResultVar { get; set; } protected override void CacheMetadata(NativeActivityMetadata metadata) { base.CacheMetadata(metadata); Predicate = new VisualBasicValue&lt;TResult&gt;("ExpressionText.Length"); ResultVar = new Variable&lt;TResult&gt;("ResultVar"); Assign = new Assign { To = new OutArgument&lt;TResult&gt;(ResultVar), Value = new InArgument&lt;TResult&gt;(Predicate) }; metadata.AddImplementationVariable(ResultVar); metadata.AddImplementationChild(Assign); } protected override void Execute(NativeActivityContext context) { // this line, commented or not, is the same! Predicate.ExpressionText = ExpressionText.Get(context); context.ScheduleActivity(Assign, new CompletionCallback(AssignComplete)); } private void AssignComplete(NativeActivityContext context, ActivityInstance completedInstance) { // the result will always be the ExpressionText.Length Result.Set(context, ResultVar.Get(context)); } } </code></pre> <p>When you get at <code>Execute()</code> method changing the child implementation has no effect. The execution mode is on and the children tree cannot be altered. </p>
    singulars
    1. This table or related slice is empty.
    1. POWF4: How do I evaluate an expression only known at runtime?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USJoao
    1. USJoao
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. COAs the title of this question mentions, the expression is not known at all before runtime. This is basically for a rule engine where the user specifies the condition as a VB.NET expression stored as a string in the database.
      singulars
      1. PO
      1. USAllon Guralnek
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload