FromSql query parameter name collisions

[mikary]

When queries with multiple query sources having calls to FromSql with parameters generate SQL, the query parameter names are not unique and an exception is thrown.

[Fact]
public virtual void From_sql_queryable_multiple_composed_with_parameters_and_closure_parameters()
{
    var city = "London";
    var startDate = new DateTime(1997, 1, 1);
    var endDate = new DateTime(1998, 1, 1);

    using (var context = CreateContext())
    {
        var actual
            = (from c in context.Set<Customer>().FromSql("SELECT * FROM Customers WHERE City = {0}", city)
                from o in context.Set<Order>().FromSql("SELECT * FROM Orders WHERE OrderDate BETWEEN {0} AND {1}",
                startDate,
                endDate)
                where c.CustomerID == o.CustomerID
                select new { c, o })
                .ToArray();
    }
}

Test 'Microsoft.Data.Entity.SqlServer.FunctionalTests.FromSqlQuerySqlServerTest.From_sql_queryable_multiple_composed_with_parameters_and_closure_parameters' failed:
    System.Data.SqlClient.SqlException : The variable name '@p0' has already been declared. Variable names must be unique within a query batch or stored procedure.
Must declare the scalar variable "@p1".
    at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
    at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
    at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
    at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
    at System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
    at System.Data.SqlClient.SqlDataReader.get_MetaData()
    at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
    at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
    at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)
    at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
    at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
    at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
    at System.Data.Common.DbCommand.ExecuteReader()
    Query\QueryingEnumerable.cs(79,0): at Microsoft.Data.Entity.Relational.Query.QueryingEnumerable.Enumerator.MoveNext()
    at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
    at System.Linq.Enumerable.<SelectManyIterator>d__1`2.MoveNext()
    at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
    Query\LinqOperatorProvider.cs(144,0): at Microsoft.Data.Entity.Query.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()
    at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
    at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
    FromSqlQueryTestBase.cs(133,0): at Microsoft.Data.Entity.Relational.FunctionalTests.FromSqlQueryTestBase`1.From_sql_queryable_multiple_composed_with_parameters_and_closure_parameters()
    FromSqlQuerySqlServerTest.cs(13,0): at Microsoft.Data.Entity.SqlServer.FunctionalTests.FromSqlQuerySqlServerTest.From_sql_queryable_multiple_composed_with_parameters_and_closure_parameters()