Another way to evaluate the Length (+ obj). Length

When binding an ASP. Net page, if the title exceeds 20, it is omitted. General Practice:
Eval ("Title") = null? "" :( Eval ("Title"). ToString (). Length <= 20? Eval ("Title"). ToString (): Eval ("Title"). ToString (). Substring (0, 17) + "... ")

 

Let me explain the results first and look at the common methods in the ASP era:

("" + Eval ("Title"). Length <= 20? ("" + Eval ("Title") :( "" + Eval ("Title"). Substring () + "... "

 

Well, my expression is a little bad. In fact, I want to demonstrate a method to avoid null and ToString, that is, "" + obj

 

Some people disagree and think this is a bad usage. In addition, if obj is not a String, there is a null exception and the performance is poor ......

 

Let's test

If obj is not a String, there is no null exception.

Let's take a look at the IL next to it.

In fact, the compiler has handled it, for example: String. Concat (obj). Note that here is a static method of the Object parameter, which is not a commonly used two parameter

 

Let's take a look at this mysterious String. Concat (Object)

Oh, after a lap, I still came back!

 

The result shows that "" + obj and obj = null? "": Obj. ToString () is exactly the same!
New Life Development Team