using System;
using System.ComponentModel;
using System.Data;

namespace AIMSExtension
{
    public class TypeHelper
    {

        public static Type ConvertTypeToBaseType(Type t)
        {

            //判断convertsionType类型是否为泛型，因为nullable是泛型类, 
            //判断convertsionType是否为nullable泛型类
            if (t.IsGenericType &&( t.GetGenericTypeDefinition().Equals(typeof(Nullable<>))|| t.GetGenericTypeDefinition().Equals(typeof(DBNull))))
            {
                //如果convertsionType为nullable类，声明一个NullableConverter类，该类提供从Nullable类到基础基元类型的转换
                NullableConverter nullableConverter = new NullableConverter(t);
                //将convertsionType转换为nullable对的基础基元类型
                t = nullableConverter.UnderlyingType;
            }
            return t;
        }

        public static object GetDefalutValue(Type t)
        {
            if (t.IsGenericType && t.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
            {
                return null;
            }
            var code = Type.GetTypeCode(t);
           
            switch (code)
            {
                case TypeCode.Boolean:
                    return default(bool);
                case TypeCode.Byte:
                    return default(byte);
                case TypeCode.DateTime:
                    return default(DateTime);
                case TypeCode.Decimal:
                    return default(decimal);
                case TypeCode.Double:
                    return default(double);
                case TypeCode.Int16:
                    return default(Int16);
                case TypeCode.Int32:
                    return default(Int32);
                case TypeCode.Int64:
                    return default(Int64);
                case TypeCode.SByte:
                    return default(SByte);
                case TypeCode.Single:
                    return default(Single);
                case TypeCode.String:
                    return default(String);
                case TypeCode.UInt16:
                    return default(UInt16);
                case TypeCode.UInt32:
                    return default(UInt32);
                case TypeCode.UInt64:
                    return default(UInt64);
                case TypeCode.Object:
                    return null;
                default:
                    return null;
            }

        }

            public static SqlDbType ConvertTypeToSqlDbType(Type t)
        {

            //判断convertsionType类型是否为泛型，因为nullable是泛型类, 
            //判断convertsionType是否为nullable泛型类
            if (t.IsGenericType && t.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
            {
                //如果convertsionType为nullable类，声明一个NullableConverter类，该类提供从Nullable类到基础基元类型的转换
                NullableConverter nullableConverter = new NullableConverter(t);
                //将convertsionType转换为nullable对的基础基元类型
                t = nullableConverter.UnderlyingType;
            }
            var code = Type.GetTypeCode(t);


            switch (code)
            {
                case TypeCode.Boolean:
                    return SqlDbType.Bit;
                case TypeCode.Byte:
                    return SqlDbType.TinyInt;
                case TypeCode.DateTime:
                    return SqlDbType.DateTime;
                case TypeCode.Decimal:
                    return SqlDbType.Decimal;
                case TypeCode.Double:
                    return SqlDbType.Float;
                case TypeCode.Int16:
                    return SqlDbType.SmallInt;
                case TypeCode.Int32:
                    return SqlDbType.Int;
                case TypeCode.Int64:
                    return SqlDbType.BigInt;
                case TypeCode.SByte:
                    return SqlDbType.TinyInt;
                case TypeCode.Single:
                    return SqlDbType.Real;
                case TypeCode.String:
                    return SqlDbType.NVarChar;
                case TypeCode.UInt16:
                    return SqlDbType.SmallInt;
                case TypeCode.UInt32:
                    return SqlDbType.Int;
                case TypeCode.UInt64:
                    return SqlDbType.BigInt;
                case TypeCode.Object:
                    return SqlDbType.Variant;
                default:
                    if (t == typeof(byte[]))
                    {
                        return SqlDbType.Binary;
                    }
                    return SqlDbType.Variant;

            }
        }



       
    }
}