Test Multiple_occurrences_of_SqlQuery_with_db_parameter_adds_parameter_only_once has two SqlQueryRaw invocations with two different DbParameter instances, which have the same name:

var city = "Seattle";
var qqlQuery = context.Database.SqlQueryRaw<UnmappedCustomer>(
    NormalizeDelimitersInRawString(@"SELECT * FROM [Customers] WHERE [City] = {0}"),
    CreateDbParameter("city", city));

var query = qqlQuery.Intersect(qqlQuery);

The test ensures that only one parameter actually gets sent to the database, but this is wrong if there's some parameter facet that differs between the two (e.g. Size). Since there's (probably?) no reliable way to compare DbParameters across providers, and detecting this doesn't seem too important, we should probably just send two parameters instead. The same is true of FromSql.

/cc @ajcvickers