C# DataTable 和List之间相互转换的方法

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;
 }

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，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);