/// <summary>
/// 表转实体
/// </summary>
/// <typeparam name="TEntity"></typeparam>
/// <param name="table"></param>
/// <returns></returns>
public static List <TEntity> ConvertToEntityList <TEntity>(System.Data.DataTable dataTable)
{
List <TEntity> list = new List <TEntity>();
if (dataTable == null || dataTable.Rows.Count == 0)
{
return(list);
}
// 创建行转换器
TableEntityBuilder <TEntity> builder = TableEntityBuilder <TEntity> .CreateBuilder(dataTable);
// 遍历每一行进行转换
foreach (DataRow dr in dataTable.Rows)
{
list.Add(builder.Build(dr));
}
return(list);
}
public static TableEntityBuilder <T> CreateBuilder(DataTable table)//, PropertyInfo[] props)
{
PropertyInfo[] props = typeof(T).GetProperties();
DataTable parentTable = table;
TableEntityBuilder <T> dynamicBuilder = new TableEntityBuilder <T>();
//定义一个名为DynamicCreate的动态方法，返回值typof(T)，参数typeof(DataRow)
DynamicMethod method = new DynamicMethod("DynamicCreate", typeof(T), new Type[] { typeof(DataRow) }, typeof(T), true);
ILGenerator generator = method.GetILGenerator(); //创建一个MSIL生成器，为动态方法生成代码
LocalBuilder result = generator.DeclareLocal(typeof(T)); //声明指定类型的局部变量 可以T t;这么理解
//T t=new T() 构造实体实例
generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes));
generator.Emit(OpCodes.Stloc, result);
for (int i = 0; i < parentTable.Columns.Count; i++)
{
PropertyInfo pInfo = null;
string fieldName = string.Empty;
foreach (PropertyInfo p in props)
{
EntityAttribute[] attrs = (EntityAttribute[])p.GetCustomAttributes(typeof(EntityAttribute), true);
if (attrs.Length > 0 && attrs[0].FieldName.ToLower() == parentTable.Columns[i].ColumnName.ToLower())
{
pInfo = p;
fieldName = attrs[0].FieldName;
break;
}
else if (p.Name.ToLower() == parentTable.Columns[i].ColumnName.ToLower())
{
pInfo = p;
fieldName = p.Name;
break;
}
}
System.Reflection.Emit.Label endIfLabel = generator.DefineLabel();
//实体存在该属性 且该属性有SetMethod方法
if (pInfo != null && pInfo.GetSetMethod() != null)
{
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, isDBNullMethod);//调用IsDBNull方法 如果IsDBNull==true contine
generator.Emit(OpCodes.Brtrue, endIfLabel);
/*If the value in the data reader is not null, the code sets the value on the object.*/
generator.Emit(OpCodes.Ldloc, result);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldstr, fieldName);
generator.Emit(OpCodes.Callvirt, getValueMethod);//调用get_Item方法
Type memberType = pInfo.PropertyType;
Type nullUnderlyingType = Nullable.GetUnderlyingType(memberType);
Type unboxType = nullUnderlyingType != null ? nullUnderlyingType : memberType;
if (unboxType == typeof(byte[]) || unboxType == typeof(string))
{
generator.Emit(OpCodes.Castclass, memberType);
}
else
{
if (unboxType == typeof(int) || unboxType == typeof(double) || unboxType == typeof(decimal))// || unboxType == typeof(decimal?))
{
generator.Emit(OpCodes.Call, ConvertMethods[unboxType]);
}
else
{
generator.Emit(OpCodes.Unbox_Any, parentTable.Columns[i].DataType);
//if (nullUnderlyingType != null)
//{
// generator.Emit(OpCodes.Newobj, memberType.GetConstructor(new[] { nullUnderlyingType }));
//}
}
if (nullUnderlyingType != null)
{
generator.Emit(OpCodes.Newobj, memberType.GetConstructor(new[] { nullUnderlyingType }));
}
}
generator.Emit(OpCodes.Callvirt, pInfo.GetSetMethod());//给该属性设置对应值
generator.MarkLabel(endIfLabel);
}
}
generator.Emit(OpCodes.Ldloc, result); //加载返回结果到
generator.Emit(OpCodes.Ret); //方法结束，返回
//完成动态方法的创建，并且创建执行该动态方法的委托，赋值到全局变量handler,handler在Build方法里Invoke
dynamicBuilder.handler = (Load)method.CreateDelegate(typeof(Load));
return(dynamicBuilder);
}
