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;
}
}
}