ArgumentException was unhandled

Question

I develop one for the WPF.
After I debug the code I get the following error: and happen in this line of code

An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll

Additional information: Format of the initialization string does not conform to specification starting at index 0. 
and here is my C# code:

no idea what wrong of my code.

 

connectionString="Data Source=C:\Program Files\Microsoft SQL Server\MSSQL11.SQLEXPRESS\MSSQL\DATA; initial Catalog=ETDB;Integrated Security=True"

providerName="System.Data.SqlClient" />