C# DataTable 和List之间相互转换的方法

一、List/IEnumerable转换到DataTable/DataView

方法一：

/// <summary>
/// Convert a List{T} to a DataTable.
/// </summary>
private DataTable ToDataTable<T>(List<T> items)
{
var tb = new DataTable(typeof (T).Name);

PropertyInfo[] props = typeof (T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

foreach (PropertyInfo prop in props)
{
Type t = GetCoreType(prop.PropertyType);
tb.Columns.Add(prop.Name, t);
}

foreach (T item in items)
{
var values = new object[props.Length];

for (int i = 0; i < props.Length; i++)
{
values[i] = props[i].GetValue(item, null);
}

tb.Rows.Add(values);
}

return tb;
}

/// <summary>
/// Determine of specified type is nullable
/// </summary>
public static bool IsNullable(Type t)
{
return !t.IsValueType || (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>));
}

/// <summary>
/// Return underlying type if type is Nullable otherwise return the type
/// </summary>
public static Type GetCoreType(Type t)
{
if (t != null && IsNullable(t))
{
if (!t.IsValueType)
{
return t;
}
else
{
return Nullable.GetUnderlyingType(t);
}
}
else
{
return t;
}
}

方法二：

public static DataTable ToDataTable<T>(IEnumerable<T> collection)
{
var props = typeof(T).GetProperties();
var dt = new DataTable();
dt.Columns.AddRange(props.Select(p => new DataColumn(p.Name, p.PropertyType)).ToArray());
if (collection.Count() > 0)
{
for (int i = 0; i < collection.Count(); i++)
{
ArrayList tempList = new ArrayList();
foreach (PropertyInfo pi in props)
{
object obj = pi.GetValue(collection.ElementAt(i), null);
tempList.Add(obj);
}
object[] array = tempList.ToArray();
dt.LoadDataRow(array, true);
}
}
return dt;
}

二、DataTable转换到List

方法一:

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);
}

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 T CreateItem<T>(DataRow row)
{
T obj = default(T);
if (row != null)
{
obj = Activator.CreateInstance<T>();

foreach (DataColumn column in row.Table.Columns)
{
PropertyInfo prop = obj.GetType().GetProperty(column.ColumnName);
try
{
object value = row[column.ColumnName];
prop.SetValue(obj, value, null);
}
catch
{  //You can log something here
//throw;
}
}
}

return obj;
}

 

方法二:

把查询结果以DataTable返回很方便，但是在检索数据时又很麻烦，没有模型类型检索方便。

所以很多人都是按照以下方式做的：

// 获得查询结果
DataTable dt = DbHelper.ExecuteDataTable(...);
// 把DataTable转换为IList<UserInfo>
IList<UserInfo> users = ConvertToUserInfo(dt);

问题：如果此系统有几十上百个模型，那不是每个模型中都要写个把DataTable转换为此模型的方法吗?

解决：能不能写个通用类，可以把DataTable转换为任何模型，呵呵，这就需要利用反射和泛型了

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Reflection;
namespace NCL.Data
{
/// <summary>
/// 实体转换辅助类
/// </summary>
public class ModelConvertHelper<T> where   T : new()
{
public static IList<T> ConvertToModel(DataTable dt)
{
// 定义集合
IList<T> ts = new List<T>();

// 获得此模型的类型
Type type = typeof(T);
string tempName = "";

foreach (DataRow dr in dt.Rows)
{
T t = new T();
// 获得此模型的公共属性
PropertyInfo[] propertys = t.GetType().GetProperties();
foreach (PropertyInfo pi in propertys)
{
tempName = pi.Name;  // 检查DataTable是否包含此列

if (dt.Columns.Contains(tempName))
{
// 判断此属性是否有Setter
if (!pi.CanWrite) continue;

object value = dr[tempName];
if (value != DBNull.Value)
pi.SetValue(t, value, null);
}
}
ts.Add(t);
}
return ts;
}
}
}

使用方式：

// 获得查询结果
DataTable dt = DbHelper.ExecuteDataTable(...);
// 把DataTable转换为IList<UserInfo>
IList<UserInfo> users = ModelConvertHelper<UserInfo>.ConvertToModel(dt);

来源：北大青鸟