/// <summary>
/// Determines whether the specified <see cref="System.Object" />, is equal to this instance.
/// </summary>
/// <param name="obj">The <see cref="System.Object" /> to compare with this instance.</param>
/// <returns>
/// <c>true</c> if the specified <see cref="System.Object" /> is equal to this instance; otherwise, <c>false</c>.
/// </returns>
public override bool Equals(object obj)
{
BuilderKey builderKey = obj as BuilderKey;
if (builderKey == null)
{
return(false);
}
if (_dbType != builderKey._dbType)
{
return(false);
}
if (_destinationType != builderKey._destinationType)
{
return(false);
}
if (this._dataRecordNames.Count != builderKey._dataRecordNames.Count)
{
return(false);
}
for (int i = 0; i < _dataRecordNames.Count; i++)
{
if (this._dataRecordNames[i] != builderKey._dataRecordNames[i])
{
return(false);
}
}
return(true);
}
public delegate object Build(IDataRecord dataRecord);//最终执行动态方法的一个委托
/// <summary>
/// emit绑定IDataRecord到实体类集合
/// </summary>
/// <param name="dataRecord">IDataRecord</param>
/// <param name="destinationType">实体类类型</param>
/// <param name="dbType">数据库类型(为兼容不同数据库，待完善)</param>
/// <returns></returns>
public static Build CreateBuilder(IDataRecord dataRecord, Type destinationType, DataBaseType dbType)
{
BuilderKey builderKey = new BuilderKey(destinationType, dataRecord, dbType);
Build dynamicBuilder = (Build)cache[builderKey];
if (dynamicBuilder != null)
{
return(dynamicBuilder);
}
DynamicMethod method = new DynamicMethod("DynamicCreate", destinationType, new Type[] { typeof(IDataRecord) }, destinationType, true);
ILGenerator il = method.GetILGenerator();
LocalBuilder result = il.DeclareLocal(destinationType);
il.Emit(OpCodes.Newobj, destinationType.GetConstructor(Type.EmptyTypes)); //创建目标类型实例
il.Emit(OpCodes.Stloc, result);
il.BeginExceptionBlock(); //try
for (int i = 0; i < dataRecord.FieldCount; i++)
{
PropertyInfo propertyInfo = destinationType.GetProperty(dataRecord.GetName(i),
BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);
if (propertyInfo != null && propertyInfo.GetSetMethod(true) != null)
{
Label endIfLabel = il.DefineLabel();
/* 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.
*/
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldc_I4, i);
il.Emit(OpCodes.Callvirt, isDBNullMethod);
il.Emit(OpCodes.Brtrue, endIfLabel);
//If the value in the data reader is not null, the code sets the value on the object.
il.Emit(OpCodes.Ldloc, result);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldc_I4, i);
il.Emit(OpCodes.Callvirt, getValueMethod);
Type propertyType = propertyInfo.PropertyType;
Type nullableUnderlyingType = Nullable.GetUnderlyingType(propertyType);
Type propertyBaseType = nullableUnderlyingType != null ? nullableUnderlyingType : propertyType;
if (propertyType == charType) //char类型特殊
{
il.EmitCall(OpCodes.Call, getCharValueMethod, null);
}
else if (propertyType == byteArrayType) //byte[]
{
il.Emit(OpCodes.Castclass, dataRecord.GetFieldType(i));
}
else if (propertyType.FullName == LinqBinary)
{
il.Emit(OpCodes.Unbox_Any, byteArrayType);
il.Emit(OpCodes.Newobj, propertyType.GetConstructor(new Type[] { byteArrayType }));
}
else if (dbType == DataBaseType.Oracle && propertyBaseType == boolType) //oracle数据库bool类型转换
{
il.EmitCall(OpCodes.Call, getOracleBoolValueMethod, null);
}
else if (propertyBaseType == guidType && (dbType == DataBaseType.OleDb || dbType == DataBaseType.SQLite))
{
//支持access或sqlite数据库是Guid类型和字符串类型保存的Guid类型数据转换
if (dataRecord.GetFieldType(i) != stringType)
{
il.Emit(OpCodes.Call, convertToString);
}
il.Emit(OpCodes.Newobj, propertyBaseType.GetConstructor(new Type[] { stringType })); //转为Guid类型
if (nullableUnderlyingType != null) //赋值到Nullable类型
{
il.Emit(OpCodes.Newobj, propertyType.GetConstructor(new Type[] { propertyBaseType }));
}
}
else
{
if (nullableUnderlyingType != null) //可空类型(Nullable)
{
if (propertyBaseType.IsEnum)
{
il.Emit(OpCodes.Call, convertToInt32);
}
else
{
MethodInfo convertMethod = typeof(Convert).GetMethod("To" + propertyBaseType.Name, new Type[] { objectType });
if (convertMethod != null)
{
il.Emit(OpCodes.Call, convertMethod);//将数据库类型强制转换为实体类定义的类型
}
else
{
il.Emit(OpCodes.Unbox_Any, propertyBaseType);//Guid类型无Convert转换方法
}
}
il.Emit(OpCodes.Newobj, propertyType.GetConstructor(new Type[] { propertyBaseType }));
}
else
{
if (propertyBaseType.IsEnum) //支持数据库是char和int类型的枚举转换
{
il.Emit(OpCodes.Call, convertToString); //先转为string类型,防止特殊情况,如数据库是char类型存储
il.Emit(OpCodes.Call, convertToInt32); //再转为int类型
}
else
{
MethodInfo convertMethod = typeof(Convert).GetMethod("To" + propertyBaseType.Name, new Type[] { objectType });
if (convertMethod != null)
{
il.Emit(OpCodes.Call, convertMethod);//强制转换，可能会出现类型转换异常
}
else
{
il.Emit(OpCodes.Unbox_Any, dataRecord.GetFieldType(i));//Guid
}
}
}
}
/*The last part of the code returns the value of the local variable*/
il.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod(true));
il.MarkLabel(endIfLabel);
}
}
il.BeginCatchBlock(typeof(InvalidCastException)); //catch
il.Emit(OpCodes.Rethrow);
il.BeginCatchBlock(typeof(System.Exception)); //catch
il.Emit(OpCodes.Rethrow);
il.EndExceptionBlock(); //end catch
il.Emit(OpCodes.Ldloc, result);
il.Emit(OpCodes.Ret);
dynamicBuilder = (Build)method.CreateDelegate(typeof(Build));
cache[builderKey] = dynamicBuilder;
return(dynamicBuilder);
}