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POC# Instantiate class which implements generic interface
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  1. POC# Instantiate class which implements generic interface
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    copied!<p>I have some business classes which implements <code>IBusinessRequest&lt;T&gt;</code>, for example:</p> <pre><code>public class PersonBusiness : IBusinessRequest&lt;Person&gt; { } </code></pre> <p>Besides this I have a function:</p> <pre><code> TypeHelper.CreateBusinessInstance(Type businessType, Type businessRequestType) </code></pre> <p>A requirement of a business class is that they must have a parameterless constructor, which I check in the <code>TypeHelper.CreateBusinessInstance</code> function.</p> <p>I want to create a instance of type businessType (which is <code>PersonBusiness</code>) with the generic value <code>businessRequestType</code> for <code>IBusinessRequest&lt;&gt;</code>.</p> <p>How can I get this done?</p> <p>EDIT1:</p> <p>Thanks for all answers it putted me on the right track. The situation I wrote down was not the real situation I was dealing with. I hoped it was just enough to solve my problem :-)</p> <p>I now came up with the following, which works like charm.</p> <pre><code>public interface IBusinessRequest&lt;T&gt; where T : class { T Request { get; set; } } public interface IBusiness { /// &lt;summary&gt; /// Validates the request against custom rules /// &lt;/summary&gt; /// &lt;param name="meldingen"&gt;Return a list of validation messages&lt;/param&gt; /// &lt;returns&gt;returns true is validation went succesfull, false when something is wrong&lt;/returns&gt; bool Validate(out List&lt;string&gt; meldingen); /// &lt;summary&gt; /// Executes business logic and returns a response object. /// &lt;/summary&gt; /// &lt;returns&gt;The strongly typed response object&lt;/returns&gt; object Execute(object request); } public class PersonBusiness :IBusiness, IBusinessRequest&lt;Person&gt; { } public static IBusiness CreateBusinessInstance(Type type, object requestMessage) { //some checks on the type, like: is of IBusiness &amp; IBusinessRequest&lt;&gt; ... //get al constructors of type ConstructorInfo[] constructors = type.GetConstructors(); //if we have more then one constructor throw error if (constructors.Length &gt; 1) { throw new BusinessCreateException(String.Format(PrivateErrors.ToManyConstructorsInTypeError, type, constructors.Length, 1)); } //constructor parameters ParameterInfo[] parameterInfo = constructors[0].GetParameters(); //we do not allow a constructor with more then one parameters. if (parameterInfo.Length &gt; 0) { throw new BusinessCreateException(String.Format(PrivateErrors.ConstructorHasToManyParametersError, type, 0)); } IBusiness instance = null; try { //create an instance, invoke constructor with zero parameters object invokeResult = constructors[0].Invoke(new object[0]); //set property "Request" PropertyInfo pi = type.GetProperty("Request"); //do we have found a property if (pi != null) { pi.SetValue(invokeResult, requestMessage ,null); } instance = invokeResult as IBusiness; } catch (Exception ex) { throw new BusinessCreateException(String.Format(PrivateErrors.BusinessCreateError, type.FullName), ex); } //return result return instance; } </code></pre> <p>Now at runtime in a other part of the sofware the business class type is given to me (i.e PersonBusiness). Another fact is the part that I know the requestMessage which is the same that is given to IBusinessRequest. I need this requestMessage to set the property Request of the PersonBusiness class (which is implemented from IRequestMessage)</p> <p>These two variables I give to static IBusiness CreateBusinessInstance(Type type, object requestMessage) which gives me back the IBusiness, which i further use to execute some business function.</p> <p>Thanks all!</p> <p>Gr</p> <p>Martijn</p>
 

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