database - 获取数据库数据类型 ServiceStack Ormlite

Question

有没有办法从 POCO 类中获取各种属性的实际数据库数据类型？例如:让我们假设 POCO 类

public  class Product : IHasId<int>
{
    [Alias("id")]
    [Required]
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description  { get; set; }
}

字段名称和描述可以是数据库中的 Varchar(n) 或文本 (SQL Server)。是否可以从 POCO 属性中获取实际的数据库数据类型？

Answer 1

OrmLite 期望底层 RDBMS 架构列定义是 TypeConverter 中指定的内容，您可以使用它来获取:

var converter = OrmLiteConfig.DialectProvider.GetStringConverter();
var columnDef = converter.ColumnDefinition;

要获得实际的列定义，您需要使用自定义 SQL 来查询 SQL Server

var sql = @"select COLUMN_NAME, data_type + 
    case
        when data_type like '%text' or data_type like 'image' or data_type like 'sql_variant' or data_type like 'xml'
            then ''
        when data_type = 'float'
            then '(' + convert(varchar(10), isnull(numeric_precision, 18)) + ')'
        when data_type = 'numeric' or data_type = 'decimal'
            then '(' + convert(varchar(10), isnull(numeric_precision, 18)) + ',' + convert(varchar(10), isnull(numeric_scale, 0)) + ')'
        when (data_type like '%char' or data_type like '%binary') and character_maximum_length = -1
            then '(max)'
        when character_maximum_length is not null
            then '(' + convert(varchar(10), character_maximum_length) + ')'
        else ''
    end as COLUMN_DEFINITION
FROM information_schema.columns";

using (var db = dbFactory.OpenDbConnection())
{
    var results = db.Dictionary<string,string>(sql + " WHERE table_name = 'Product'");

    var nameColumnDef = results["Name"]; //= varchar(8000)

    //Or print out all column definitions for each field with:
    results.PrintDump();
    /*
    {
        Id: int,
        Name: varchar(8000)
        ...
    }
    */
}