What difference does .AsNoTracking() make?

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I have a question regarding the .AsNoTracking() extension, as this is all quite new and quite confusing.

I’m using a per-request context for a website.

A lot of my entities don’t change so don’t need to be tracked, but I have the following scenario where I’m unsure of what’s going to the database, or even whether it makes a difference in this case.

This example is what I’m currently doing:

context.Set<User>().AsNoTracking()
// Step 1) Get user
context.Set<User>()
// Step 2) Update user

This is the same as above but removing the .AsNoTracking() from Step 1:

context.Set<User>();
// Step 1) Get user
context.Set<User>()
// Step 2) Update user

The Steps 1 & 2 use the same context but occur at different times. What I can’t work out is whether there is any difference. As Step 2 is an update I’m guessing both will hit the database twice anyway.

Can anyone tell me what the difference is?

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