1. Add ADO.NET model does not appear when connecting MYSQL:
a. confirmation mysql-for-visualstudio-1.2.7.msi is installed
b. Make sure .net version is 4.6
2. The connection has been selected, but inexplicably disappeared in the next time:
a. Verify that the project references mysql.data version currently installed mysql-connector-net version are the same
b. 6.9.10 version is recommended