Dynamic.cs: Yummy Linq Goodness
Posted on August 20, 2008While testing out some more asp.net mvc stuff, I came up with a need to order a list of objects by property name(a string value). Assuming I have a list of customers named customerList, i want to do something like: customerList.OrderBy("FirstName"), and get back a list of customers sorted by the FirstName property of each customer instance in the list.
Originally, I used something based on this post. It looked like this:
public IEnumerable<TModel> OrderBy(string propertyName, bool sortAscending){
if (String.IsNullOrEmpty(propertyName))
throw new ArgumentNullException("propertyName");
PropertyInfo property = typeof(TModel).GetProperty(propertyName);
if (property == null)
throw new NullReferenceException(
String.Format("property '{0}' was not found on type '{1}'",
propertyName,
typeof(TModel).Name));
if (sortAscending)
return _models.OfType<TModel>().OrderBy(mo => property.GetValue(mo, null));
else
return _models.OfType<TModel>().OrderByDescending(mo => property.GetValue(mo, null));
}
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But then I found dynamic.cs located in the DynamicQuery project in the CSharpSamples.zip file. Wicked cool shizzle. Now that method above looks like this:
public IEnumerable<TModel> OrderBy(string propertyName, Sort sortDirection){
if (String.IsNullOrEmpty(propertyName))
throw new ArgumentNullException("propertyName");
return _models.AsQueryable<TModel>()
.OrderBy(propertyName, sortDirection.ToString());
}
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Now using my updated code looks like this:
IEnumerable<Customer> customers = customerRepository.OrderBy("FirstName", Sort.Descending);
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I had to dig a little for this, but the signature on OrderBy, one of them anyway, looks like this:
IQueryable<T> OrderBy<T>(string ordering, params object[] values)
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To use this, pass in the property name in the first spot, and "Ascending" or "Descending" in the second spot, like this:
customerList.AsQueryable<Customer>().OrderBy("FirstName", "Descending")
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I felt like sticking the OrderBy method on my IRepository interface which, using your favorite subversion tool, can be checked out here:
http://svn.chrisjcarter.com/public/EPS
There's some really cool geeky code in dynamic.cs, check it out.
