Solution to the problem of keyword not supported data source

When using the Entity Framework, if the connection string in the configuration file is not written correctly, this exception will be thrown. Moreover, when you modify the configuration file and press crtl + s to save, you will be prompted in the output window. The solution is to correct your connection string again. The correct format is as follows

<add name="testEntities" 
     connectionString="metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;provider=System.Data.SqlClient;provider connection string="data source=(local);initial catalog=test;integrated security=True;multipleactiveresultsets=True;App=EntityFramework"" 
     providerName="System.Data.EntityClient" />

Read More: