Change Entity Framework ConnectionString‎

Problem: 
- Dynamically change Entity Framework Connection String‎
- How to change the connection string in the EntityFramework ...
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- Cannot change the connectionstring with Entity Framework 4.1 code ...
- Entity Framework - how can I change connection string to be relative?
- Entity Framework Connection String Trouble - Stack Overflow

Solution:
Just add System.Configuration.dll to Refrences of your Project and then use of this code

ConfigurationManager.ConnectionStrings[0].ConnectionString = blah blah blah
ConfigurationManager.ConnectionStrings["XYZEntities"].ConnectionString = blah blah blah

Error in Solution:
Error: 
The configuration is read only.
Correction: 

var Configuration = ConfigurationManager.ConnectionStrings["amaBoxOfficeEntities"];
typeof(ConfigurationElement).GetField("_bReadOnly", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(Configuration, false);
Configuration.ConnectionString = blah blah blah