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POGeneric List of OrderBy Lambda
 

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    <p>I am trying to build a generic query mechanism to access my repository. I wish to use Lambda expressions to filter and sort the query. I am struggling to find a way to pass a list of generic Lambda expressions in, specifically for the order-by, and would appreciate help in doing so.</p> <p>EDIT: 2 requirements I am trying to meet is, not expose IQueryable beyond the repository, but still be able to carry out some filtering and sorting at database level.</p> <p>To better illustrate this let me show you the code</p> <pre><code>public class Query&lt;T&gt; { public class OrderBy&lt;T&gt; { public Expression&lt;Func&lt;T, **int**&gt;&gt; Clause { set; get; } // Order By clause public bool Descending = true; } public Expression&lt;Func&lt;T, bool&gt;&gt; Where { set; get; } // Where clause public IList&lt;OrderBy&lt;T&gt;&gt; OrderBys { set; get; } // Where clause public Query() { OrderBys = new List&lt;OrderBy&lt;T&gt;&gt;(); } } public IEnumerable&lt;Person&gt; FindBy(Query&lt;Person&gt; query) { IQueryable&lt;Person&gt; Temp = GetObjectSet(); if (query.Where != null) Temp = Temp.Where(query.Where); foreach (var OrderByThis in query.OrderBys) { if (OrderByThis.Descending) Temp = Temp.OrderByDescending(OrderByThis.Clause); else Temp = Temp.OrderBy(OrderByThis.Clause); } return Temp.ToList&lt;Person&gt;(); } </code></pre> <p>This is all very nice, BUT Expression&lt; Func&lt; T, <strong>int</strong>>> is not generic. I need to be able to do something like:</p> <pre><code>Query&lt;Person&gt; query = new Query&lt;Person&gt;(); Query&lt;Person&gt;.OrderBy&lt;Person&gt; clause1 = new Query&lt;Person&gt;.OrderBy&lt;Person&gt;(); clause1.Clause = m =&gt; m.Username; Query&lt;Person&gt;.OrderBy&lt;Person&gt; clause2 = new Query&lt;Person&gt;.OrderBy&lt;Person&gt;(); clause2.Clause = m =&gt; m.DateOfBirth; query.OrderBys.Add(clause1); query.OrderBys.Add(clause2); </code></pre> <p>i.e. adding a number of different fields of different types.</p> <p>I imagine there must be a way to store these as generic Lambda functions, and then in the repository convert then to the strongly typed Lambda function it needs.</p> <p>How can I do this?</p>
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    1. CO.NET already provides mechanisms for ordering and sorting, with extension methods like `.OrderBy` and `.Where` and a much cleaner syntax. Why not just expose something like `repository.Get(Func<IEnumerable<Person>,IEnumerable<Person> queryExpression)`? (or make it `Expression<Func…` if you need to parse the expression tree)
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      1. USJay
    2. COI don't quite follow sorry, can give a concrete example?
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    3. COCan you use `object` as your type?
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