[AttributeUsage(AttributeTargets.Class|AttributeTargets.Method)]    public class DbFunAttribute : Attribute    {        public DbFunAttribute( string functionName, Type returnType)        {            ReturnType = returnType;            FunctionName = functionName;        }        public DbFunAttribute()        {        }        public Type ReturnType { get; set; }        public string FunctionName { get; set; }    }    public static class SqlFunctionExtension    {        public static ModelBuilder UseSqlFunction(this ModelBuilder modelBuilder)        {            foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())            {                foreach (var type in assembly.GetTypes()                .Where(item=>item.GetCustomAttribute
     
      () != null))                {                    List
      
        funList = type.GetMethods(BindingFlags.Public | BindingFlags.Static)                        .Where(method => method.GetCustomAttribute
       
        () != null)                        .ToList();                    foreach (var method in funList)                    {                        modelBuilder.HasDbFunction(method).HasTranslation(arg =>                        {                            var argumentos = arg.ToList();                            var attribute = method.GetCustomAttribute
        
         ();                            var funcionName = attribute.FunctionName;                            return new SqlFunctionExpression(                                funcionName,                                attribute.ReturnType,                                argumentos);                        });                    }                }            }            return modelBuilder;        }    }
        
       
      
     

调用的Sql方法

[DbFun]    public class Function    {        public static int DateDiff(string part, DateTime inicio, DateTime fim)            => 0;        [DbFun("REPLACE", typeof(string))]        public static string Replace(object dados, string substituir, string por)            => string.Empty;    }

 

启用

Ef的DbContext对象下面的

protected override void OnModelCreating(ModelBuilder modelBuilder)        {            base.OnModelCreating(modelBuilder);            modelBuilder.HasDbFunction(typeof(Function).GetMethod("DateDiff")).HasTranslation((arg =>            {                var argumentos = arg.ToList();                argumentos[0] = new SqlFragmentExpression((string)((ConstantExpression)argumentos.First()).Value);                return new SqlFunctionExpression(                    "DATEDIFF",                    typeof(int),                    argumentos);            }));            modelBuilder.UseSqlFunction();}

调用

var serviceProvider = services.BuildServiceProvider();            var context = serviceProvider.GetService(typeof(CoreWebContext)) as CoreWebContext;            var query = context.EntityOrder.Where(item => Function.DateDiff("MONTH", DateTime.Parse("2018-06-01"), item.PayTime.Value) == 0).Select(item =>                Function.Replace(item.OrderNo, "2018", "xyzx")            );            var list = query.ToList();