将DataTable转换为List，将List转换为DataTable的实现类

Posted 2020-10-07 Chavez.net

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace Xmh.DBUnit
{
    /// <summary>
    ///  将DataTable转换为List，将List转换为DataTable的实现类
    /// </summary>
    public static class DataTableHelper
    {
        public static DataTable ConvertTo<T>(IList<T> list)
        {
            DataTable table = CreateTable<T>();
            Type entityType = typeof(T);
            PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);
            foreach (T item in list)
            {
                DataRow row = table.NewRow();
                foreach (PropertyDescriptor prop in properties)
                    row[prop.Name] = prop.GetValue(item);
                table.Rows.Add(row);
            }
            return table;
        }

        public static IList<T> ConvertTo<T>(IList<DataRow> rows)
        {
            IList<T> list = null;
            if (rows != null)
            {
                list = new List<T>();
                foreach (DataRow row in rows)
                {
                    T item = CreateItem<T>(row);
                    list.Add(item);
                }
            }
            return list;
        }

        public static IList<T> ConvertTo<T>(DataTable table)
        {
            if (table == null)
                return null;

            List<DataRow> rows = new List<DataRow>();
            foreach (DataRow row in table.Rows)
                rows.Add(row);

            return ConvertTo<T>(rows);
        }

        //Convert DataRow into T Object
        public static T CreateItem<T>(DataRow row)
        {
            string columnName;
            T obj = default(T);
            if (row != null)
            {
                obj = Activator.CreateInstance<T>();
                foreach (DataColumn column in row.Table.Columns)
                {
                    columnName = column.ColumnName;
                    //Get property with same columnName
                    PropertyInfo prop = obj.GetType().GetProperty(columnName);

                    try
                    {
                        Type type = prop.PropertyType;
                        //判断type类型是否为泛型，因为nullable是泛型类,  
                        if (type.IsGenericType && type.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))//判断convertsionType是否为nullable泛型类  

                        {
                            //如果type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  
                            System.ComponentModel.NullableConverter nullableConverter = new System.ComponentModel.NullableConverter(type);
                            //将type转换为nullable对的基础基元类型  
                            type = nullableConverter.UnderlyingType;
                        }
                        //Get value for the column
                        object value = (row[columnName].GetType() == typeof(DBNull))
                        ? null : row[columnName];
                        //Set property value
                        if (prop.CanWrite)    //判断其是否可写
                            prop.SetValue(obj, (value == null ? null : Convert.ChangeType(value, type)), null);
                    }
                    catch
                    {
                        throw;
                        //Catch whatever here
                    }
                }
            }
            return obj;
        }

        public static DataTable CreateTable<T>()
        {
            Type entityType = typeof(T);
            DataTable table = new DataTable(entityType.Name);
            PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);

            foreach (PropertyDescriptor prop in properties)
                table.Columns.Add(prop.Name, prop.PropertyType);

            return table;
        }

        public static List<T> ToList<T>(this DataTable dt) where T : class, new()
        {
            Type t = typeof(T);
            PropertyInfo[] propertys = t.GetProperties();
            List<T> lst = new List<T>();
            string typeName = string.Empty;
            foreach (DataRow dr in dt.Rows)
            {
                T entity = new T();
                foreach (PropertyInfo pi in propertys)
                {
                    typeName = pi.Name;
                    if (dt.Columns.Contains(typeName))
                    {
                        if (!pi.CanWrite) continue;
                        object value = dr[typeName];
                        if (value == DBNull.Value) continue;
                        if (pi.PropertyType == typeof(string))
                        {
                            pi.SetValue(entity, value.ToString(), null);
                        }
                        else if (pi.PropertyType == typeof(int) || pi.PropertyType == typeof(int?))
                        {
                            pi.SetValue(entity, int.Parse(value.ToString()), null);
                        }
                        else if (pi.PropertyType == typeof(DateTime?) || pi.PropertyType == typeof(DateTime))
                        {
                            pi.SetValue(entity, DateTime.Parse(value.ToString()), null);
                        }
                        else if (pi.PropertyType == typeof(float))
                        {
                            pi.SetValue(entity, float.Parse(value.ToString()), null);
                        }
                        else if (pi.PropertyType == typeof(double))
                        {
                            pi.SetValue(entity, double.Parse(value.ToString()), null);
                        }
                        else
                        {
                            pi.SetValue(entity, value, null);
                        }
                    }
                }
                lst.Add(entity);
            }
            return lst;
        }
    }
}