/// <summary>
/// 根据参数条件筛选数据
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="sql"></param>
/// <param name="param"></param>
/// <returns></returns>
public IEnumerable <T> Query <T>(string sql, dynamic param,
IDbConnection conn, IDbTransaction transaction) where T : class
{
CacheInfo cacheInfo = new CacheInfo();
if (param != null)
{
var identity = new Identity(sql, CommandType.Text, conn, null, param == null ? null : param.GetType(), null);
cacheInfo.ParamReader = SqlCached.CreateParamInfoGenerator(identity, false);
}
IDbCommand cmd = null;
try
{
cmd = SetupCommand(sql, cacheInfo.ParamReader, param, CommandType.Text, conn, transaction);
IDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
DynamicBuilder <T> builder = DynamicBuilder <T> .CreateBuilder(reader);
yield return(builder.Build(reader));
}
reader.Close();
}
finally
{
if (cmd != null)
{
cmd.Dispose();
}
}
}
/// <summary>
/// 数据查询方法
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="cmd"></param>
/// <returns></returns>
public IEnumerable <T> Query <T>(IDbCommand cmd, IDbConnection conn, IDbTransaction transaction) where T : class
{
try
{
cmd.Connection = conn;
cmd.Transaction = transaction;
IDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
DynamicBuilder <T> builder = DynamicBuilder <T> .CreateBuilder(reader);
yield return(builder.Build(reader));
}
reader.Close();
}
finally
{
if (cmd != null)
{
cmd.Dispose();
}
}
}
/// <summary>
/// 得到一个创建者
/// </summary>
/// <param name="dataRecord"></param>
/// <returns></returns>
public static DynamicBuilder <T> CreateBuilder(IDataRecord dataRecord)
{
int entityTypeHashCode = typeof(T).GetHashCode();
lock (_LOCK){
if (_FULLENTITY_MAP.ContainsKey(entityTypeHashCode))
{
return(_FULLENTITY_MAP[entityTypeHashCode] as DynamicBuilder <T>);
}
}
DynamicBuilder <T> dynamicBuilder = new DynamicBuilder <T>();
//定义一个名为'DynamicCreate'的动态方法，返回值typof(T)，参数typeof(IDataRecord),与typeof(IDataRecord)逻辑关联{动态方法可以访问类型的所有成员。 },
DynamicMethod method = new DynamicMethod("DynamicCreate", typeof(T),
new Type[] { typeof(IDataRecord) }, typeof(T), true);
//创建一个MSIL生成器，为动态方法生成代码
ILGenerator generator = method.GetILGenerator();
//为动态方法声明指定类型T的局部变量 T result;
LocalBuilder result = generator.DeclareLocal(typeof(T));
//The next piece of code instantiates the requested type of object and stores it in the local variable.
//可以t=new T();这么理解
generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes));
generator.Emit(OpCodes.Stloc, result);
for (int i = 0; i < dataRecord.FieldCount; i++)
{
PropertyInfo propertyInfo = typeof(T).GetProperty(dataRecord.GetName(i));//根据列名取属性 原则上属性和列是一一对应的关系
Label endIfLabel = generator.DefineLabel();
if (propertyInfo != null && propertyInfo.GetSetMethod() != null)//实体存在该属性 且该属性有SetMethod方法
{
/*The code then loops through the fields in the data reader, finding matching properties on the type passed in.
* When a match is found, the code checks to see if the value from the data reader is null.
*/
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, isDBNullMethod);//就知道这里要调用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.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, getValueMethod);//调用get_Item方法
//处理为空数据列
Type dataType = dataRecord.GetFieldType(i);
bool isNullable = false;
if (propertyInfo.PropertyType.Name.ToLower().Contains("nullable"))
{
isNullable = true;
}
if (isNullable)
{
generator.Emit(OpCodes.Unbox_Any, GetNullableType(dataType));
}
else
{
generator.Emit(OpCodes.Unbox_Any, dataType);
}
generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());//给该属性设置对应值
generator.MarkLabel(endIfLabel);
}
}
/*The last part of the code returns the value of the local variable*/
generator.Emit(OpCodes.Ldloc, result);
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));
lock (_LOCK){
if (_FULLENTITY_MAP.ContainsKey(entityTypeHashCode) == false)
{
_FULLENTITY_MAP.Add(entityTypeHashCode, dynamicBuilder);
}
}
return(dynamicBuilder);
}
