OMS.NET/DbClass/SqlHelper.cs

using System.Reflection;
using MySql.Data.MySqlClient;
using OMS.NET.Common;
namespace OMS.NET.DbClass{
    [AttributeUsage(AttributeTargets.Class, Inherited = false)]
    public class TableAttribute : Attribute
    {
        public string TableName { get; }
        public TableAttribute(string tableName)
        {
            TableName = tableName;
        }
    }

    [AttributeUsage(AttributeTargets.Property, Inherited = false)]
    public class ColumnAttribute : Attribute
    {
        public string ColumnName { get; }
        public bool IsPrimaryKey { get; }

        public bool IsIdentity { get; } // 是否自增列
        public ColumnAttribute(string columnName, bool isPrimaryKey = false, bool isIdentity = false)
        {
            ColumnName = columnName;
            IsPrimaryKey = isPrimaryKey;
            IsIdentity = isIdentity;
        }
    }

    public class SqlHelper{
        public static string GetTableName(Type type)
        {
            var attr = type.GetCustomAttribute<TableAttribute>();
            return attr?.TableName ?? throw new Exception($"{type.Name} 没有指定数据表");
        }

        public static IEnumerable<PropertyInfo> GetProperties(Type type)
        {
            return type.GetProperties()
                       .Where(p => p.GetCustomAttribute<ColumnAttribute>() != null);
        }

        private static PropertyInfo GetPrimaryKeyProperties(Type type)
        {
            var primaryKeyProperties = GetProperties(type)
                .Where(p => p.GetCustomAttribute<ColumnAttribute>()?.IsPrimaryKey == true)
                .ToList();

            if (primaryKeyProperties.Count == 0)
            {
                throw new InvalidOperationException("No primary key defined for the class.");
            }

            if (primaryKeyProperties.Count != 1)
            {
                throw new InvalidOperationException("Multiple primary keys defined for the class. Only one primary key is allowed.");
            }

            return primaryKeyProperties.First();
        }

        private static IEnumerable<PropertyInfo> GetNonKeyProperties(Type type)
        {
            return GetProperties(type)
                .Where(p => p.GetCustomAttribute<ColumnAttribute>()?.IsPrimaryKey == false);
        }

        private static PropertyInfo? GetIdentityKeyProperty(Type type)
        {
            var primaryKey = GetPrimaryKeyProperties(type);
            return (primaryKey.GetCustomAttribute<ColumnAttribute>()!.IsIdentity == true) ? null : primaryKey;
        }

        public static string GetInsertSql(Type type)
        {
            var tableName = GetTableName(type);
            var identityKey = GetIdentityKeyProperty(type);
            var columns = GetNonKeyProperties(type)
                .Select(p => p.GetCustomAttribute<ColumnAttribute>()!.ColumnName).ToList();
            var values = GetNonKeyProperties(type)
                .Select(p => "@" + p.Name).ToList();

            if (identityKey != null)
            {
                // Exclude the identity key from columns and values for insert statement
                columns.Add(identityKey.GetCustomAttribute<ColumnAttribute>()!.ColumnName);
                values.Add("@" + identityKey.Name);
            }

            return $"INSERT INTO {tableName} ({string.Join(", ", columns)}) VALUES ({string.Join(", ", values)})";
        }

        public static string GetUpdateSql(Type type)
        {
            var tableName = GetTableName(type);
            var setClause = string.Join(", ",
                GetNonKeyProperties(type)
                .Select(p => $"{p.GetCustomAttribute<ColumnAttribute>()!.ColumnName} = @{p.Name}"));
            var primaryKey = GetPrimaryKeyProperties(type);
            var whereClause = $"{primaryKey.GetCustomAttribute<ColumnAttribute>()!.ColumnName} = @{primaryKey.Name}";

            return $"UPDATE {tableName} SET {setClause} WHERE {whereClause}";
        }

        public static string GetDeleteSql(Type type)
        {
            var tableName = GetTableName(type);
            var primaryKey = GetPrimaryKeyProperties(type);
            var whereClause = $"{primaryKey.GetCustomAttribute<ColumnAttribute>()!.ColumnName} = @{primaryKey.Name}";

            return $"DELETE FROM {tableName} WHERE {whereClause}";
        }

        public static string GetSelectSql(Type type)
        {
            var tableName = GetTableName(type);
            var columns = string.Join(", ",
                GetProperties(type)
                .Select(p => p.GetCustomAttribute<ColumnAttribute>()!.ColumnName));

            return $"SELECT {columns} FROM {tableName}";
        }

        public static string GetSelectSqlWithPrimaryKey(Type type)
        {
            var tableName = GetTableName(type);
            var columns = string.Join(", ",
                GetProperties(type)
                .Select(p => p.GetCustomAttribute<ColumnAttribute>()!.ColumnName));
            var primaryKey = GetPrimaryKeyProperties(type);
            var whereClause = $"{primaryKey.GetCustomAttribute<ColumnAttribute>()!.ColumnName} = @{primaryKey.Name}";

            return $"SELECT {columns} FROM {tableName} WHERE {whereClause}";
        }

        public static IEnumerable<T> SelectAll<T>() where T : SqlTable, new()
        {
            var type = typeof(T);
            var selectSql = GetSelectSql(type);

            using MySqlConnection connection = new(GlobalArea.ConnectionStringWithDbName);
            connection.Open(); // 确保在执行命令之前打开连接
            using var command = new MySqlCommand(selectSql, connection);
            using var reader = command.ExecuteReader();
            var results = new List<T>();
            while (reader.Read())
            {
                var item = new T();
                PopulateObject(reader, item);
                results.Add(item);
            }
            return results;
        }

        private static void PopulateObject(MySqlDataReader reader, SqlTable obj)
        {
            var type = obj.GetType();
            foreach (var property in GetProperties(type))
            {
                var columnAttr = property.GetCustomAttribute<ColumnAttribute>()!;
                var value = reader[columnAttr.ColumnName];
                if (value != DBNull.Value)
                {
                    property.SetValue(obj, Convert.ChangeType(value, property.PropertyType));
                }
            }
        }

        public static T? Get<T>(object key) where T : SqlTable, new()
        {
            var type = typeof(T);
            var selectSql = GetSelectSqlWithPrimaryKey(type);
            using MySqlConnection connection = new(GlobalArea.ConnectionStringWithDbName);
            connection.Open(); // 确保在执行命令之前打开连接
            using var command = new MySqlCommand(selectSql, connection);
            var primaryKey = GetPrimaryKeyProperties(type);
            command.Parameters.AddWithValue("@" + primaryKey.GetCustomAttribute<ColumnAttribute>()!.ColumnName, key);
            using var reader = command.ExecuteReader();
            while (reader.Read())
            {
                var item = new T();
                PopulateObject(reader, item);
                return item;
            }
            return null;
        }
    }
}