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POCombine some lambda expressions using Or operand
 

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  1. POCombine some lambda expressions using Or operand
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    <p>I want to make a dynamic expression which will be generated out of an unknown number of <code>Or</code> conditions:</p> <pre><code> IQueryable&lt;Entity&gt; entities = Repository&lt;Entity&gt;.Load(); Expression&lt;Func&lt;Entity, bool&gt;&gt; wholeFilter; foreach(condition in Conditions) { Expression&lt;Func&lt;Entity, bool&gt;&gt; filter = e =&gt; e.something1 == condition.First &amp;&amp; e.something2 == condition.Second wholeFilter = wholeFilter.Or(filter) } return entities.Where(wholeFilter); </code></pre> <p>I tried to implement the <code>Or</code> extension but I couldn't come up with a logical way. </p> <p>Moreover I was playing around the <a href="http://www.albahari.com/nutshell/predicatebuilder.aspx" rel="nofollow">PredicateBuilder</a> and wrote something like:</p> <pre><code>var predicate = PredicateBuilder.False&lt;Entity&gt;(); </code></pre> <p>and the code below in my loop:</p> <pre><code>predicate = predicate.Or(filter); </code></pre> <p>However I realized that it just <code>And</code> the conditions together not <code>Or</code> them....</p> <p>Any idea how to generate the combined expression?<br> regards</p> <p><strong>EDIT :</strong><br> the original code that I wrote :</p> <pre><code>public IQueryable&lt;IEntity&gt; Find(IEntityType entityType, List&lt;AdaptiveObjectModelSpecification&gt; queryObjecs) { if (entityType == null) return null; var predicate = PredicateBuilder.False&lt;IEntity&gt;(); var entities = Repository&lt;IEntity&gt;.Find(p =&gt; p.EntityType == entityType); if (queryObjecs != null) { foreach (var queryObject in queryObjecs) { if (entityType.PropertyTypes.Count(p =&gt; p.PropertyName == queryObject.PropertyType.PropertyName) == 0) throw new MissingFieldException(String.Format("Column {0} not found.", queryObject.PropertyType.PropertyName)); predicate = predicate.Or(e =&gt; e.Properties.Any(p =&gt; p.Value == queryObject.SearchValue &amp;&amp; p.PropertyType.PropertyName == queryObject.PropertyType.PropertyName)); } entities = entities.Where(predicate); } return entities; } </code></pre> <p>generated entities.Expression.ToString() when queryObjects has two elements =</p> <pre><code>{value(NHibernate.Linq.NhQueryable`1[Azarakhsh.Domain.Core.AdaptiveObjectModel.Interface.IEntity]) .Where(p =&gt; (p.EntityType == value(Azarakhsh.Domain.Core.AdaptiveObjectModel.Service.AdaptiveObjectModelRepositoryService+&lt;&gt;c__DisplayClassd).entityType)) // The line below is generated by PredicateBuilder .Where( Param_0 =&gt; ((False OrElse Invoke(e =&gt; e.Properties.Any(p =&gt; ((p.Value == value(Azarakhsh.Domain.Core.AdaptiveObjectModel.Service.AdaptiveObjectModelRepositoryService+&lt;&gt;c__DisplayClass10).queryObject.SearchValue) AndAlso (p.PropertyType.PropertyName == value(Azarakhsh.Domain.Core.AdaptiveObjectModel.Service.AdaptiveObjectModelRepositoryService+&lt;&gt;c__DisplayClass10).queryObject.PropertyType.PropertyName))), Param_0)) OrElse Invoke(e =&gt; e.Properties.Any(p =&gt; ((p.Value == value(Azarakhsh.Domain.Core.AdaptiveObjectModel.Service.AdaptiveObjectModelRepositoryService+&lt;&gt;c__DisplayClass10).queryObject.SearchValue) AndAlso (p.PropertyType.PropertyName == value(Azarakhsh.Domain.Core.AdaptiveObjectModel.Service.AdaptiveObjectModelRepositoryService+&lt;&gt;c__DisplayClass10).queryObject.PropertyType.PropertyName))), Param_0)))} </code></pre>
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    1. COAny reason why you never accept answers?
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      1. USAlex Aza
    2. COSorry but I assume a practical answer should be marked as "Accepted". right?
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    3. COwell, am I missing something here? it's all as I expected... no need to mention I definitely vote for a post which is relevant to finding the solution...
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