Linq dynamic order by a list with example

Sort a list dynamically is easy, in this article we will create a class to sort the source dynamically by passing source, column and sort order.

Let’s write our class and then we will see it with example, create a new class DynamicSort

public static class DynamicSort
{
  public static IQueryable<T> OrderBy<T>(this IQueryable<T> source
      , string columnName, bool isAscending = true)
  {
     if (String.IsNullOrEmpty(columnName))
     {
       return source;
     }

     ParameterExpression parameter = Expression.Parameter(source.ElementType, "");

     MemberExpression property = Expression.Property(parameter, columnName);
     LambdaExpression lambda = Expression.Lambda(property, parameter);

     string methodName = isAscending ? "OrderBy" : "OrderByDescending";

     Expression methodCallExpression = Expression.Call(typeof(Queryable), methodName,
                           new Type[] { source.ElementType, property.Type },
                           source.Expression, Expression.Quote(lambda));

     return source.Provider.CreateQuery<T>(methodCallExpression);
  }
}

How we will create a simple aspx page to test our functionality, so here is the HTML of the page

<div>
  <asp:GridView ID="gvProduct" runat="server">    
  </asp:GridView>
</div>
<div>
  Column To Sort: <asp:TextBox ID="txtColumn" runat="server" />
</div>
<div>
  <asp:CheckBox ID="chkIsAscending" runat="server" Checked="true" text="Ascending?" />
</div>
<div>
   <asp:Button ID="btnSort" runat="server" Text="Sort" onclick="btnSort_Click" />
</div>

We will create a simple class product to create a list and pass it to sort

public class Product
{
    public Int32 Id { get; set; }
    public String Name { get; set; }
    public Int32 Qty { get; set; }
}

And here is the code for button click event:

protected void btnSort_Click(object sender, EventArgs e)
{
    List<Product> products = new List<Product>();
    products.Add(new Product { Id = 1, Name = "A", Qty = 10 });
    products.Add(new Product { Id = 2, Name = "C", Qty = 10 });
    products.Add(new Product { Id = 3, Name = "E", Qty = 10 });
    products.Add(new Product { Id = 4, Name = "D", Qty = 10 });
    products.Add(new Product { Id = 5, Name = "B", Qty = 10 });


    gvProduct.DataSource = DynamicSort.OrderBy(products.AsQueryable(), 
                              txtColumn.Text, chkIsAscending.Checked);
    gvProduct.DataBind();
}

Note: we converted our proudct to Queryable by using products.AsQueryable() before passing as parameter.

As you can see we added product with rough data to test our functionality and they are not in proper order because we have class to do this. Run your application and enter column name in text and define the order by selecting/unselecting the check box and click sort, that’s it.

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