帮我书写C#与sql server的类型映射枚举类

好的，以下是C#与SQL Server的类型映射枚举类的代码：

public enum SqlType
{
    BigInt,
    Binary,
    Bit,
    Char,
    Date,
    DateTime,
    DateTime2,
    DateTimeOffset,
    Decimal,
    Float,
    Geography,
    Geometry,
    HierarchyId,
    Image,
    Int,
    Money,
    NChar,
    NText,
    Numeric,
    NVarChar,
    Real,
    SmallDateTime,
    SmallInt,
    SmallMoney,
    SqlVariant,
    SysName,
    Text,
    Time,
    Timestamp,
    TinyInt,
    UniqueIdentifier,
    VarBinary,
    VarChar,
    Xml
}

public static class SqlTypeMapper
{
    public static string Map(SqlType type)
    {
        switch (type)
        {
            case SqlType.BigInt:
                return "bigint";
            case SqlType.Binary:
                return "binary";
            case SqlType.Bit:
                return "bit";
            case SqlType.Char:
                return "char";
            case SqlType.Date:
                return "date";
            case SqlType.DateTime:
                return "datetime";
            case SqlType.DateTime2:
                return "datetime2";
            case SqlType.DateTimeOffset:
                return "datetimeoffset";
            case SqlType.Decimal:
                return "decimal";
            case SqlType.Float:
                return "float";
            case SqlType.Geography:
                return "geography";
            case SqlType.Geometry:
                return "geometry";
            case SqlType.HierarchyId:
                return "hierarchyid";
            case SqlType.Image:
                return "image";
            case SqlType.Int:
                return "int";
            case SqlType.Money:
                return "money";
            case SqlType.NChar:
                return "nchar";
            case SqlType.NText:
                return "ntext";
            case SqlType.Numeric:
                return "numeric";
            case SqlType.NVarChar:
                return "nvarchar";
            case SqlType.Real:
                return "real";
            case SqlType.SmallDateTime:
                return "smalldatetime";
            case SqlType.SmallInt:
                return "smallint";
            case SqlType.SmallMoney:
                return "smallmoney";
            case SqlType.SqlVariant:
                return "sql_variant";
            case SqlType.SysName:
                return "sysname";
            case SqlType.Text:
                return "text";
            case SqlType.Time:
                return "time";
            case SqlType.Timestamp:
                return "timestamp";
            case SqlType.TinyInt:
                return "tinyint";
            case SqlType.UniqueIdentifier:
                return "uniqueidentifier";
            case SqlType.VarBinary:
                return "varbinary";
            case SqlType.VarChar:
                return "varchar";
            case SqlType.Xml:
                return "xml";
            default:
                throw new ArgumentOutOfRangeException(nameof(type), type, null);
        }
    }
}

使用时，可以通过 `SqlTypeMapper.Map(SqlType)` 方法来获取对应的SQL Server数据类型。例如：

var sqlType = SqlTypeMapper.Map(SqlType.VarChar);

这样就可以得到 `varchar` 这个数据类型了。