Databases
StackOverflow2013
Postsdbo
POCan you get a Func<T> (or similar) from a MethodInfo object?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POCan you get a Func<T> (or similar) from a MethodInfo object?
    primarykey
    data
    text
    <p>I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.)</p> <p>Suppose there exists some class that looks like this:</p> <pre><code>public class MyClass { public string GetName() { return "My Name"; } } </code></pre> <p>Bear with me here. I know that if I have an instance of <code>MyClass</code> called <code>x</code>, I can call <code>x.GetName()</code>. Furthermore, I could set a <code>Func&lt;string&gt;</code> variable to <code>x.GetName</code>.</p> <p>Now here's my question. Let's say I <em>don't</em> know the above class is called <code>MyClass</code>; I've got some object, <code>x</code>, but I have no idea what it is. I could check to see if that object has a <code>GetName</code> method by doing this:</p> <pre><code>MethodInfo getName = x.GetType().GetMethod("GetName"); </code></pre> <p>Suppose <code>getName</code> is not null. Then couldn't I furthermore check if <code>getName.ReturnType == typeof(string)</code> and <code>getName.GetParameters().Length == 0</code>, and at this point, wouldn't I be quite certain that the method represented by my <code>getName</code> object could <em>definitely</em> be cast to a <code>Func&lt;string&gt;</code>, somehow?</p> <p>I realize there's a <code>MethodInfo.Invoke</code>, and I also realize I could always <em>create</em> a <code>Func&lt;string&gt;</code> like:</p> <pre><code>Func&lt;string&gt; getNameFunc = () =&gt; getName.Invoke(x, null); </code></pre> <p>I guess what I'm asking is if there's any way to go <strong>from</strong> a <code>MethodInfo</code> object <strong>to</strong> the actual method it represents, incurring the performance cost of reflection in the <em>process</em>, but <em>after</em> that point being able to call the method directly (via, e.g., a <code>Func&lt;string&gt;</code> or something similar) <em>without</em> a performance penalty.</p> <p>What I'm envisioning might look something like this:</p> <pre><code>// obviously this would throw an exception if GetActualInstanceMethod returned // something that couldn't be cast to a Func&lt;string&gt; Func&lt;string&gt; getNameFunc = (Func&lt;string&gt;)getName.GetActualInstanceMethod(x); </code></pre> <p>(I realize that doesn't exist; I'm wondering if there's anything <em>like</em> it.)</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USBartoszKP
    1. USDan Tao
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POCan you get a Func<T> (or similar) from a MethodInfo object?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POCan you get a Func<T> (or similar) from a MethodInfo object?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POCan you get a Func<T> (or similar) from a MethodInfo object?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COOn the comments you make in your edit - you will see a huge speed increase with solutions like this, because there's very little difference between a dynamically compiled delegate and a statically compiled one; once the overhead of the compilation is factored out. Since I 'discovered' the expression trees stuff, I've been using them all over the place, and would probably put it as my #1 feature from .Net 3.5 . In v4 it's even better as you can write multi-statement code - needed because of the extensions required by the DLR.
      singulars
      1. POCan you get a Func<T> (or similar) from a MethodInfo object?
      1. USAndras Zoltan
 

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