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POHow can I use reflection to invoke DomainService.Load method?
 

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  1. POHow can I use reflection to invoke DomainService.Load method?
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    <p>I am trying to build a utility method that will generically load entitycollections using Reflection. The idea is that a programmer using the utility can specify any type of entity and this method will discover the correct EntityQuery and the load the context with what they requested. So, I have collected the Entity type and Where clause from the user, now I am trying to figure out how to invoke the method. Here is what I have:</p> <pre><code>public void Handle(LoadEntityQuery loadQuery, Action&lt;LoadEntityQueryResult&gt; reply) { foreach (var entry in loadQuery.Entities) { Type entityType = entry.Key; Type _contextType = EmployeeJobsContext.Instance.GetType(); MethodInfo _methodInfo = (from x in _contextType.GetMethods() where x.ReturnType.BaseType == typeof(EntityQuery) from y in x.ReturnType.GetGenericArguments() where y == entityType select x).FirstOrDefault(); if (_methodInfo != null) { var query = _methodInfo.Invoke(EmployeeJobsContext.Instance, null); var _loadMethods = from x in _contextType.GetMethods() where x.Name == "Load" &amp;&amp; x.GetParameters().Length == 3 select x; MethodInfo _loadMethod = null; if (_loadMethods != null) { foreach (MethodInfo item in _loadMethods) { ParameterInfo[] _paramInfo = item.GetParameters(); if (_paramInfo[0].ParameterType.BaseType == typeof(EntityQuery) &amp;&amp; _paramInfo[1].ParameterType.IsGenericType &amp;&amp; _paramInfo[1].ParameterType.GetGenericArguments().Length == 1 &amp;&amp; _paramInfo[1].ParameterType.GetGenericArguments()[0].BaseType == typeof(LoadOperation) &amp;&amp; _paramInfo[2].ParameterType == typeof(object)) { _loadMethod = item; break; } } } MethodInfo _loadOpMethod = this.GetType().GetMethod("LoadOperationResult"); Delegate d = Delegate.CreateDelegate(typeof(LoadOpDel), _loadOpMethod); if (_loadMethod != null) { object [] _params = new object[3]; _params[0] = query; _params[1] = d; _params[2] = null; _loadMethod = _loadMethod.MakeGenericMethod(entityType); _loadMethod.Invoke(_context, _params); } } } } public delegate void LoadOpDel(LoadOperation loadOp); public void LoadOperationResult (LoadOperation loadOp) { if (loadOp.HasError == true) { //reply(new LoadEntityQueryResult { Error = loadOp.Error.Message }); loadOp.MarkErrorAsHandled(); } } </code></pre> <p>The foreach loop is iterating a Dictionary>>, where the Key is an Entity type and the value is a Where clause. The first part of code is finding the correct EntityQuery method and invoking it to get the actual query. It then discovers the correct Load overload (I know, likely there is a better way to find the method :) ) This portion of the code works correctly, I am able to discover the correct EntityQuery and the Load method. </p> <p>For the LoadOperation, I want to use the LoadOperationResult as my delegate method. When I try to run this code however, I receive an exception stating that the delegate type and the method type signatures do not match. I am pretty sure my signature is correct because if I was to call Load directly and pass the function name as the callback normally, this code would execute properly. I am fairly familiar with reflective programming, however throwing Generics and Action callbacks into the mix is a bit above my level at this point. I'm at a loss as to what I am doing wrong, does anyone have any pointers for me? Am I way off? Thanks for your help!! Jason</p>
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    1. USRockdocta
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      1. POHow can I use reflection to invoke DomainService.Load method?
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    1. COSo the exception is thrown at `_loadMethod.Invoke(_context, _params);` or when you are creating the delegate? And I also may be confused about this, but don't you want to create your delegate outside of the loop?
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      1. POHow can I use reflection to invoke DomainService.Load method?
      1. USSteve Mallory
    2. COSorry, I did not specify whenthis occurs. I get the exception when I create the delegate.also, I need the delegate to be created in the loop since the load operation is called for every entity in the collection.
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      1. POHow can I use reflection to invoke DomainService.Load method?
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