为什么在DisplayNameFor（）中需要lambda表达式？

Question

For the example code:

<th>@Html.DisplayNameFor(model => model.Artist.Name)</th>

Why is the lambda expression necessary at all? Why can't it just be

<th>@Html.DisplayNameFor(model.Artist.Name)</th>

Answer 1

This is trickery using expression trees.

The first constructs an expression tree at runtime, allowing the method to go in and find the member being accessed (and thus get all of its attributes).

The second would simply pass the value of Name into the method.

Answer 2

Remember that your model is simply a definition of your general data structure, and this is bound at runtime to determine what the actual values of the model should be set to, dependent on the parameters being used to access the data.

What you're seeing is just the way that the DisplayNameFor method is defined in order for this to happen, and your 2nd line of code is simply invalid. DisplayNameFor is an extension method of the HTML helper, and accepts as a single parameter a lambda expression that identifies the model and the property of the model that you want to display, so that the actual data retrieval can occur at runtime. See here for the formal definition of the method:

https://msdn.microsoft.com/en-us/library/hh833697(v=vs.118).aspx