C#中DataTable与List<T>的互转

╰+哭是因爲堅強的太久メ 2021-09-16 13:46 407阅读 0赞

**1、创建DataTable扩展方法类（DataTableExtend.cs）**

using System;
    using System.Collections.Generic;
    using System.Data;
    using System.Reflection;
    
    namespace MyTest.OA.Common
    {
        /// <summary>
        /// DataTable扩展方法类
        /// </summary>
        public static class DataTableExtend
        {
            /// <summary>
            /// DataTable转成List
            /// </summary>
            public static List<T> ToDataList<T>(this DataTable dt)
            {
                var list = new List<T>();
                var plist = new List<PropertyInfo>(typeof(T).GetProperties());
    
                if (dt == null || dt.Rows.Count == 0)
                {
                    return null;
                }
    
                foreach (DataRow item in dt.Rows)
                {
                    T s = Activator.CreateInstance<T>();
                    for (int i = 0; i < dt.Columns.Count; i++)
                    {
                        PropertyInfo info = plist.Find(p => p.Name == dt.Columns[i].ColumnName);
                        if (info != null)
                        {
                            try
                            {
                                if (!Convert.IsDBNull(item[i]))
                                {
                                    object v = null;
                                    if (info.PropertyType.ToString().Contains("System.Nullable"))
                                    {
                                        v = Convert.ChangeType(item[i], Nullable.GetUnderlyingType(info.PropertyType));
                                    }
                                    else
                                    {
                                        v = Convert.ChangeType(item[i], info.PropertyType);
                                    }
                                    info.SetValue(s, v, null);
                                }
                            }
                            catch (Exception ex)
                            {
                                throw new Exception("字段[" + info.Name + "]转换出错," + ex.Message);
                            }
                        }
                    }
                    list.Add(s);
                }
                return list;
            }
    
            /// <summary>
            /// DataTable转成实体对象
            /// </summary>
            /// <typeparam name="T"></typeparam>
            /// <param name="dt"></param>
            /// <returns></returns>
            public static T ToDataEntity<T>(this DataTable dt)
            {
                T s = Activator.CreateInstance<T>();
                if (dt == null || dt.Rows.Count == 0)
                {
                    return default(T);
                }
                var plist = new List<PropertyInfo>(typeof(T).GetProperties());
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    PropertyInfo info = plist.Find(p => p.Name == dt.Columns[i].ColumnName);
                    if (info != null)
                    {
                        try
                        {
                            if (!Convert.IsDBNull(dt.Rows[0][i]))
                            {
                                object v = null;
                                if (info.PropertyType.ToString().Contains("System.Nullable"))
                                {
                                    v = Convert.ChangeType(dt.Rows[0][i], Nullable.GetUnderlyingType(info.PropertyType));
                                }
                                else
                                {
                                    v = Convert.ChangeType(dt.Rows[0][i], info.PropertyType);
                                }
                                info.SetValue(s, v, null);
                            }
                        }
                        catch (Exception ex)
                        {
                            throw new Exception("字段[" + info.Name + "]转换出错," + ex.Message);
                        }
                    }
                }
                return s;
            }
    
            /// <summary>
            /// List转成DataTable
            /// </summary>
            /// <typeparam name="T">实体类型</typeparam>
            /// <param name="entities">实体集合</param>
            public static DataTable ToDataTable<T>(List<T> entities)
            {
                if (entities == null || entities.Count == 0)
                {
                    return null;
                }
    
                var result = CreateTable<T>();
                FillData(result, entities);
                return result;
            }
    
            /// <summary>
            /// 创建表
            /// </summary>
            private static DataTable CreateTable<T>()
            {
                var result = new DataTable();
                var type = typeof(T);
                foreach (var property in type.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
                {
                    var propertyType = property.PropertyType;
                    if ((propertyType.IsGenericType) && (propertyType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        propertyType = propertyType.GetGenericArguments()[0];
                    result.Columns.Add(property.Name, propertyType);
                }
                return result;
            }
    
            /// <summary>
            /// 填充数据
            /// </summary>
            private static void FillData<T>(DataTable dt, IEnumerable<T> entities)
            {
                foreach (var entity in entities)
                {
                    dt.Rows.Add(CreateRow(dt, entity));
                }
            }
    
            /// <summary>
            /// 创建行
            /// </summary>
            private static DataRow CreateRow<T>(DataTable dt, T entity)
            {
                DataRow row = dt.NewRow();
                var type = typeof(T);
                foreach (var property in type.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
                {
                    row[property.Name] = property.GetValue(entity) ?? DBNull.Value;
                }
                return row;
            }
        }
    }

**2、其它代码**

2.1 创建用户信息类（UserInfo.cs）

/// <summary>
    /// 用户信息类
    /// </summary>
    public class UserInfo
    {
        /// <summary>
        /// 编号
        /// </summary>
        public int ID { get; set; }
    
        /// <summary>
        /// 名称
        /// </summary>
        public string Name { get; set; }
    
        /// <summary>
        /// 年龄
        /// </summary>
        public int Age { get; set; }
    
        /// <summary>
        /// 成绩
        /// </summary>
        public double Score { get; set; }
    
        /// <summary>
        /// 创建时间
        /// </summary>
        public DateTime? CreateTime { get; set; }
    }

2.2 创建DataTable对象的方法

/// <summary>
    /// 创建DataTable对象
    /// </summary>
    public static DataTable CreateDataTable()
    {
        //创建DataTable
        DataTable dt = new DataTable("NewDt");
                
        //创建自增长的ID列
        DataColumn dc = dt.Columns.Add("ID", Type.GetType("System.Int32"));
        dc.AutoIncrement = true;   //自动增加
        dc.AutoIncrementSeed = 1;  //起始为1
        dc.AutoIncrementStep = 1;  //步长为1
        dc.AllowDBNull = false;    //非空
    
        //创建其它列表
        dt.Columns.Add(new DataColumn("Name", Type.GetType("System.String")));
        dt.Columns.Add(new DataColumn("Age", Type.GetType("System.Int32")));
        dt.Columns.Add(new DataColumn("Score", Type.GetType("System.Decimal")));
        dt.Columns.Add(new DataColumn("CreateTime", Type.GetType("System.DateTime")));
    
        //创建数据
        DataRow dr = dt.NewRow();
        dr["Name"] = "张三";
        dr["Age"] = 28;
        dr["Score"] = 85.5;
        dr["CreateTime"] = DateTime.Now;
        dt.Rows.Add(dr);
    
        dr = dt.NewRow();
        dr["Name"] = "李四";
        dr["Age"] = 24;
        dr["Score"] = 72;
        dr["CreateTime"] = DateTime.Now;
        dt.Rows.Add(dr);
    
        dr = dt.NewRow();
        dr["Name"] = "王五";
        dr["Age"] = 36;
        dr["Score"] = 63.5;
        dr["CreateTime"] = DateTime.Now;
        dt.Rows.Add(dr);
    
        return dt;
    }

**3、测试**

3.1 添加引用：

using MyTest.OA.Common;

3.2 测试方法：

//创建一个DataTable对象
    DataTable dt = CreateDataTable();
    
    //1、DataTable转成List
    List<UserInfo> userList = dt.ToDataList<UserInfo>();
    
    //2、DataTable转成实体对象
    UserInfo user = dt.ToDataEntity<UserInfo>();
    
    //3、List转成DataTable
    DataTable dt2 = DataTableExtend.ToDataTable<UserInfo>(userList);