private void Prepare(IDataRecord dataRecord)
{
// 定义一个动态方法，返回类型 typeof(T)，输入类型 typeof(IDataRecord)
Type type = typeof(T);
string name = string.Format("Create{0}", type.Name);
DynamicMethod dynamicMethod;
if (DynamicMethodContainer.IsExist(name))
{
dynamicMethod = DynamicMethodContainer.Get(name);
}
else
{
Dictionary <string, int> dictionary = Match(dataRecord);
dynamicMethod = new DynamicMethod(
name,
type,
new Type[] { typeof(IDataRecord) },
type,
true);
// 创建一个MSIL生成器，为动态方法生成代码
ILGenerator generator = dynamicMethod.GetILGenerator();
// 声明指定类型的局部变量，可以理解为 T t;
LocalBuilder localBuilder = generator.DeclareLocal(type);
// 可以理解为 T t = new T(); The next piece of code instantiates the requested type of object and stores it in the local variable.
ConstructorInfo constructorInfo = type.GetConstructor(Type.EmptyTypes);
generator.Emit(OpCodes.Newobj, constructorInfo);
generator.Emit(OpCodes.Stloc, localBuilder);
foreach (string propertyName in dictionary.Keys)
{
PropertyInfo propertyInfo = type.GetProperty(propertyName);
int index = dictionary[propertyName];
// 定义标签
Label endIfLabel = generator.DefineLabel();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, index);
// 调用 Callvirt : dataRecord.IsDBNull() 方法
generator.Emit(OpCodes.Callvirt, isDBNullMethod);
// 如果是 DataRecord.IsDBNull() == true 则 contine
generator.Emit(OpCodes.Brtrue, endIfLabel);
generator.Emit(OpCodes.Ldloc, localBuilder);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, index);
// 调用 Callvirt : dataRecord.get_Item(i) 方法
generator.Emit(OpCodes.Callvirt, getItemMethod);
generator.Emit(OpCodes.Unbox_Any, dataRecord.GetFieldType(index));
// 调用 Callvirt : propertyInfo.GetSetMethod 方法
generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
// 在当前 MSIL 流位置进行标记
generator.MarkLabel(endIfLabel);
}
// The last part of the code returns the value of the local variable
generator.Emit(OpCodes.Ldloc, localBuilder);
// 方法结束
generator.Emit(OpCodes.Ret);
DynamicMethodContainer.Add(name, dynamicMethod);
}
// 完成动态方法的创建并创建执行该动态方法的委托
// DataRecord2Entity 在 Build 方法里实现
this.dataRecord2Entity = (DataRecord2Entity)dynamicMethod.CreateDelegate(typeof(DataRecord2Entity));
}
/// 定义一个动态方法，返回类型 typeof(T)，输入类型 typeof(IDataRecord)
/// <remarks>
/// if (DynamicMethodContainer.IsExist(name))
/// {
/// DynamicMethod dynamicMethod = DynamicMethodContainer.Get(name);
/// }
/// else
/// {
/// DynamicMethodContainer.Add(name, dynamicMethod);
/// }
/// </remarks>
protected void PrepareDelegate(IDataRecord dataRecord)
{
string name = string.Format("Create{0}", this.type.Name);
Type[] parameterTypes = new Type[] { typeof(IDataRecord) };
DynamicMethod dynamicMethod = new DynamicMethod(name, this.type, parameterTypes, this.type, true);
// 创建一个MSIL生成器，为动态方法生成代码
ILGenerator generator = dynamicMethod.GetILGenerator();
// 声明指定类型的局部变量，可以理解为 T t;
LocalBuilder localBuilder = generator.DeclareLocal(this.type);
// PUSH : T t = new T();
// Instantiates the requested type of object and stores it in the local variable.
ConstructorInfo constructorInfo = type.GetConstructor(Type.EmptyTypes);
generator.Emit(OpCodes.Newobj, constructorInfo);
generator.Emit(OpCodes.Stloc, localBuilder);
Dictionary <int, string> dictionary = this.Match(dataRecord);
foreach (int i in dictionary.Keys)
{
string propertyName = dictionary[i];
PropertyInfo propertyInfo = this.type.GetProperty(propertyName);
// 定义标签
Label endIfLabel = generator.DefineLabel();
// 调用 Callvirt : IDataRecord.IsDBNull() 方法
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, IsDBNullMethod);
// 如果是 DataRecord.IsDBNull() == true 则 contine
generator.Emit(OpCodes.Brtrue, endIfLabel);
// POP : T t
generator.Emit(OpCodes.Ldloc, localBuilder);
// 调用 Callvirt : IDataRecord.get_Item(i) 方法
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, getItemMethod);
//Ad By RQ 2011-01-18 12:46 ORACLE DATE 用 dataRecord.GetFieldType(i) 得出的类型转换出错
//generator.Emit(OpCodes.Unbox_Any, dataRecord.GetFieldType(i));
generator.Emit(OpCodes.Unbox_Any, propertyInfo.PropertyType);
// 调用 Callvirt : propertyInfo.GetSetMethod 方法
generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
// 在当前 MSIL 流位置进行标记
generator.MarkLabel(endIfLabel);
}
// returns the value of the local variable
generator.Emit(OpCodes.Ldloc, localBuilder);
// 方法结束
generator.Emit(OpCodes.Ret);
// 完成动态方法的创建并创建执行该动态方法的委托
this.dataRecord2Entity = (DataRecord2Entity)dynamicMethod.CreateDelegate(typeof(DataRecord2Entity));
}
