DataTable和List之间互转
参考https://www.cnblogs.com/shiyh/p/7478241.html
Table to List
一、
static public List<T> Tolist<T>(DataTable dt) where T : class, new() { Type t = typeof(T); PropertyInfo[] PropertyInfo = t.GetProperties(); List<T> list = new List<T>(); string typeName = string.Empty; foreach (DataRow item in dt.Rows) { T obj = new T(); foreach (PropertyInfo s in PropertyInfo) { typeName = s.Name; if (dt.Columns.Contains(typeName)) { if (!s.CanWrite) continue; object value = item[typeName]; if (value == DBNull.Value) continue; if (s.PropertyType == typeof(string)) { s.SetValue(obj, value.ToString(), null); } else { s.SetValue(obj, value, null); } } } list.Add(obj); } return list; }
二、
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; }
三、利用反射和泛型,创建实体转换辅助类
调用;
IList<UserInfo> users = ModelConvertHelper<UserInfo>.ConvertToModel(dt);
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; } } }
三(1):
/// <summary> /// DateTable转为List /// </summary> /// <returns></returns> public static List<T> ToList<T>(this DataTable dt) { List<string> dataColumn = dt.Columns.Cast<DataColumn>().Select(c => c.ColumnName).ToList(); PropertyInfo[] properties = typeof(T).GetProperties(); string columnName = string.Empty; return dt.AsEnumerable().Select(row => { T t = Activator.CreateInstance<T>(); foreach (PropertyInfo p in properties) { columnName = p.Name; if (dataColumn.Contains(columnName)) { if (!p.CanWrite) continue; object value = row[columnName]; Type type = p.PropertyType; if (value != DBNull.Value) p.SetValue(t, Convert.ChangeType(value, type), null); } } return t; }).ToList(); }
四、高性能的基于Emit的
实现
/// <summary> /// 把datatable转换为对象集合列表List<T> /// </summary> public class DataTableConvert { //把DataRow转换为对象的委托声明 private delegate T Load<T>(DataRow dataRecord); //用于构造Emit的DataRow中获取字段的方法信息 private static readonly MethodInfo getValueMethod = typeof(DataRow).GetMethod("get_Item", new Type[] { typeof(int) }); //用于构造Emit的DataRow中判断是否为空行的方法信息 private static readonly MethodInfo isDBNullMethod = typeof(DataRow).GetMethod("IsNull", new Type[] { typeof(int) }); //使用字典存储实体的类型以及与之对应的Emit生成的转换方法 private static Dictionary<Type, Delegate> rowMapMethods = new Dictionary<Type, Delegate>(); public static List<T> ToList<T>(DataTable dt) { List<T> list = new List<T>(); if (dt == null) return list; //声明 委托Load<T>的一个实例rowMap Load<T> rowMap = null; //从rowMapMethods查找当前T类对应的转换方法,没有则使用Emit构造一个。 if (!rowMapMethods.ContainsKey(typeof(T))) { DynamicMethod method = new DynamicMethod("DynamicCreateEntity_" + typeof(T).Name, typeof(T), new Type[] { typeof(DataRow) }, typeof(T), true); ILGenerator generator = method.GetILGenerator(); LocalBuilder result = generator.DeclareLocal(typeof(T)); generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes)); generator.Emit(OpCodes.Stloc, result); for (int index = 0; index < dt.Columns.Count; index++) { PropertyInfo propertyInfo = typeof(T).GetProperty(dt.Columns[index].ColumnName); Label endIfLabel = generator.DefineLabel(); if (propertyInfo != null && propertyInfo.GetSetMethod() != null) { generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, index); generator.Emit(OpCodes.Callvirt, isDBNullMethod); generator.Emit(OpCodes.Brtrue, endIfLabel); generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, index); generator.Emit(OpCodes.Callvirt, getValueMethod); generator.Emit(OpCodes.Unbox_Any, propertyInfo.PropertyType); generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod()); generator.MarkLabel(endIfLabel); } } generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ret); //构造完成以后传给rowMap rowMap = (Load<T>)method.CreateDelegate(typeof(Load<T>)); } else { rowMap = (Load<T>)rowMapMethods[typeof(T)]; } //遍历Datatable的rows集合,调用rowMap把DataRow转换为对象(T) foreach (DataRow info in dt.Rows) list.Add(rowMap(info)); return list; } }
List To Tabel
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; } }
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; }
高性能的基于Emit
实现的