internal static RowMap GetTypeMap(Type mType)
{
if (!XCache.TypeMaps.TryGetValue(mType, out var map))
{
map = new RowMap(mType);
XCache.TypeMaps[mType] = map;
}
return(map);
}
private static Func <IDataReader, M> SetFunc(IDataReader reader)
{
//
var mType = typeof(M);
var dm = new DynamicMethod("MyDAL" + Guid.NewGuid().ToString(), mType, new[] { typeof(IDataReader) }, mType, true);
var il = dm.GetILGenerator();
il.DeclareLocal(typeof(int)); // 定义 loc0 int
il.DeclareLocal(mType); // 定义 loc1 M
il.Emit(OpCodes.Ldc_I4_0);
il.Emit(OpCodes.Stloc_0); // 赋值 loc0 = 0
//
var length = reader.FieldCount;
var names = Enumerable.Range(0, length).Select(i => reader.GetName(i)).ToArray();
var typeMap = CommonIL.GetTypeMap(mType);
int index = 0;
var ctor = typeMap.DefaultConstructor();
//
il.Emit(OpCodes.Newobj, ctor);
il.Emit(OpCodes.Stloc_1); // 赋值 loc1 = new M();
il.BeginExceptionBlock(); // try begin
il.Emit(OpCodes.Ldloc_1); // 加载 loc1
//
var members = names.Select(n => typeMap.GetMember(n)).ToList();
bool first = true;
var allDone = il.DefineLabel();
int enumDeclareLocal = -1;
int valueCopyLocal = il.DeclareLocal(typeof(object)).LocalIndex; // 定义 loc_object 变量, 然后返回此本地变量的index值, 其实就是截止目前, 定义了本地变量的个数
foreach (var item in members)
{
if (item != null)
{
il.Emit(OpCodes.Dup);
Label isDbNullLabel = il.DefineLabel();
Label finishLabel = il.DefineLabel();
il.Emit(OpCodes.Ldarg_0);
CommonIL.EmitInt32(il, index);
il.Emit(OpCodes.Dup);
il.Emit(OpCodes.Stloc_0);
il.Emit(OpCodes.Callvirt, XConfig.GetItem); // 获取reader读取的值, reader[index]
il.Emit(OpCodes.Dup);
CommonIL.StoreLocal(il, valueCopyLocal); // 将 reader[index]的值, 存放到本地变量 loc_object 中
Type colType = reader.GetFieldType(index); // reader[index] 的列的类型 source
Type memberType = item.MemberType(); // M[item] 的类型
if (memberType == XConfig.TC.Char || memberType == XConfig.TC.CharNull)
{
il.EmitCall(
OpCodes.Call,
typeof(CommonIL).GetMethod(
memberType == XConfig.TC.Char
? nameof(CommonIL.ReadChar)
: nameof(CommonIL.ReadNullableChar), BindingFlags.Static | BindingFlags.NonPublic),
null);
}
else
{
il.Emit(OpCodes.Dup);
il.Emit(OpCodes.Isinst, typeof(DBNull)); // 判断是否为DBNull类型, 如果是, 则跳转到 标签isDbNullLabel
il.Emit(OpCodes.Brtrue_S, isDbNullLabel);
var nullUnderlyingType = Nullable.GetUnderlyingType(memberType);
var unboxType = nullUnderlyingType?.IsEnum == true ? nullUnderlyingType : memberType;
if (unboxType.IsEnum)
{
Type numericType = Enum.GetUnderlyingType(unboxType);
if (colType == typeof(string))
{
if (enumDeclareLocal == -1)
{
enumDeclareLocal = il.DeclareLocal(typeof(string)).LocalIndex;
}
il.Emit(OpCodes.Castclass, typeof(string)); // stack is now [target][target][string]
CommonIL.StoreLocal(il, enumDeclareLocal); // stack is now [target][target]
il.Emit(OpCodes.Ldtoken, unboxType); // stack is now [target][target][enum-type-token]
il.EmitCall(OpCodes.Call, typeof(Type).GetMethod(nameof(Type.GetTypeFromHandle)), null); // stack is now [target][target][enum-type]
CommonIL.LoadLocal(il, enumDeclareLocal); // stack is now [target][target][enum-type][string]
il.Emit(OpCodes.Ldc_I4_1); // stack is now [target][target][enum-type][string][true]
il.EmitCall(OpCodes.Call, XConfig.EnumParse, null); // stack is now [target][target][enum-as-object]
il.Emit(OpCodes.Unbox_Any, unboxType); // stack is now [target][target][typed-value]
}
else
{
CommonIL.FlexibleConvertBoxedFromHeadOfStack(il, colType, unboxType, numericType);
}
if (nullUnderlyingType != null)
{
il.Emit(OpCodes.Newobj, memberType.GetConstructor(new[] { nullUnderlyingType })); // stack is now [target][target][typed-value]
}
}
else if (memberType.FullName == XConfig.TC.LinqBinary)
{
il.Emit(OpCodes.Unbox_Any, typeof(byte[])); // stack is now [target][target][byte-array]
il.Emit(OpCodes.Newobj, memberType.GetConstructor(new Type[] { typeof(byte[]) })); // stack is now [target][target][binary]
}
else
{
TypeCode dataTypeCode = Type.GetTypeCode(colType), unboxTypeCode = Type.GetTypeCode(unboxType);
if (colType == unboxType || dataTypeCode == unboxTypeCode || dataTypeCode == Type.GetTypeCode(nullUnderlyingType))
{
il.Emit(OpCodes.Unbox_Any, unboxType); // stack is now [target][target][typed-value]
}
else
{
// not a direct match; need to tweak the unbox
CommonIL.FlexibleConvertBoxedFromHeadOfStack(il, colType, nullUnderlyingType ?? unboxType, null);
if (nullUnderlyingType != null)
{
il.Emit(OpCodes.Newobj, unboxType.GetConstructor(new[] { nullUnderlyingType })); // stack is now [target][target][typed-value]
}
}
}
}
// Store the value in the property/field
if (item.Property != null)
{
il.Emit(OpCodes.Callvirt, RowMap.GetPropertySetter(item.Property, mType));
}
else
{
il.Emit(OpCodes.Stfld, item.Field); // stack is now [target]
}
il.Emit(OpCodes.Br_S, finishLabel); // stack is now [target]
il.MarkLabel(isDbNullLabel); // incoming stack: [target][target][value]
il.Emit(OpCodes.Pop); // stack is now [target][target]
il.Emit(OpCodes.Pop); // stack is now [target]
il.MarkLabel(finishLabel);
}
first = false;
index++;
}
il.Emit(OpCodes.Stloc_1); // stack is empty
il.MarkLabel(allDone);
il.BeginCatchBlock(typeof(Exception)); // stack is Exception
il.Emit(OpCodes.Ldloc_0); // stack is Exception, index
il.Emit(OpCodes.Ldarg_0); // stack is Exception, index, reader
CommonIL.LoadLocal(il, valueCopyLocal); // stack is Exception, index, reader, value
il.EmitCall(OpCodes.Call, typeof(CommonIL).GetMethod(nameof(CommonIL.ThrowDataException)), null);
il.EndExceptionBlock();
il.Emit(OpCodes.Ldloc_1); // stack is [rval]
il.Emit(OpCodes.Ret);
var funcType = Expression.GetFuncType(typeof(IDataReader), mType);
return((Func <IDataReader, M>)dm.CreateDelegate(funcType));
}