EF Core 2.2-如何使用时区SQL片段创建SQLEXPRESSION

Question

我想将方法​​映射到自定义SQL，所以

CONVERT(datetime, 
        SWITCHOFFSET(GETUTCDATE(), DATEPART(TZOFFSET, GETUTCDATE() AT TIME ZONE 'Greenwich Standard Time')))

我在我的dbcontext中添加了hasdbfunction：

modelBuilder.HasDbFunction(typeof(DbContext).GetMethod(nameof(DbContext.GetDateTime)))
        .HasTranslation(e =>
            {
                var GETUTCDATE = new SqlFunctionExpression("GETUTCDATE", typeof(DateTime));
                
                var TZOFFSET = new SqlFragmentExpression("TZOFFSET");
                var ATTIMEZONE = new SqlFragmentExpression(" AT TIME ZONE ");
                var GreenwichStandardTime = new Expression("Greenwich Standard Time"); // expression with constant?
                var EXPRESSION = new Expression(GETUTCDATE, ATTIMEZONE, GreenwichStandardTime); // expression with combine multiple exprssions?
                var DATEPART = new SqlFunctionExpression("DATEPART", typeof(int), new[] { TZOFFSET , EXPRESSION  });  // cannot create

                var SWITCHOFFSET = new SqlFunctionExpression("SWITCHOFFSET", typeof(DateTimeOffset), new[] { GETUTCDATE, DATEPART });

                var DATETIME = new SqlFragmentExpression("DATETIME");
                
                new SqlFunctionExpression("CONVERT", typeof(DateTime), new[] { DATETIME, SWITCHOFFSET });
            });

我的问题是如何创建greenwichstandardtime和expression？

Answer 1

continue