How to disconnect to an user instance database

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I am use the AttachDbFilename to connection to a .mdf file of SqlExpress
(like the example below)
After the database is attached, it will be free again until all session time
out.

But sometime I want to move the .mdf file to another place, but the .mdf is
not free.
How can I disconnect all the connections to that database immediately?
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<add name="MyDataBase" connectionString="Data Source=VMXP\SQLEXPRESS;
AttachDbFilename=C:\SqlData\Healthdb\Health.mdf;
Integrated Security=True;
User Instance=True"
providerName="System.Data.SqlClient"/>