private static Func <IDataRecord, o> getReaderConverter <o>(IDataRecord record)
{
Type typeIn = typeof(IDataRecord);
Type typeOut = typeof(o);
Delegate creator = null;
if (!_expressionReaderCache.TryGetValue(typeOut, out creator))
{
List <Expression> statements = new List <Expression>();
ParameterExpression peIn = Expression.Variable(typeIn);
ParameterExpression peOut = Expression.Variable(typeOut);
statements.Add(Expression.Assign(peOut, Expression.New(typeOut)));
Type customAttrMapper = typeof(System.Data.Linq.Mapping.ColumnAttribute);
BinaryExpression beAssignProp = null;
System.Reflection.PropertyInfo[] props = typeOut.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
foreach (System.Reflection.PropertyInfo piOut in props)
{
int columnIndex = -1;
try
{
//find column index
System.Data.Linq.Mapping.ColumnAttribute[] attrs = (System.Data.Linq.Mapping.ColumnAttribute[])piOut.GetCustomAttributes(customAttrMapper, false);
if (attrs.Length > 0)
{
columnIndex = record.GetOrdinal(attrs[0].Name);
}
else
{
columnIndex = record.GetOrdinal(piOut.Name);
}
}
catch (IndexOutOfRangeException iorEx)
{
//skip if not match to any column
continue;
}
ConstantExpression ce = Expression.Constant(columnIndex, typeof(int));
MethodCallExpression mce = null;
MemberExpression meOut = Expression.Property(peOut, piOut.Name);
if (piOut.PropertyType.IsGenericType)
{
mce = Expression.Call(peIn, typeIn.GetMethod("Get" + Nullable.GetUnderlyingType(piOut.PropertyType).Name), new Expression[] { ce });
beAssignProp = BinaryExpression.Assign(meOut, Expression.Convert(mce, piOut.PropertyType));
}
else
{
mce = Expression.Call(peIn, typeIn.GetMethod("Get" + piOut.PropertyType.Name), new Expression[] { ce });
beAssignProp = BinaryExpression.Assign(meOut, mce);
}
MethodCallExpression mceCheck = Expression.Call(peIn, typeIn.GetMethod("IsDBNull"), new Expression[] { ce });
ConditionalExpression conde = Expression.IfThen(Expression.Not(mceCheck), beAssignProp);
//statements.Add(beAssignProp);
statements.Add(conde);
}
var returnStatement = peOut;
statements.Add(returnStatement);
var body = Expression.Block(new[] { peOut }, statements.ToArray());
var lamda = Expression.Lambda <Func <IDataRecord, o> >(body, peIn);
creator = lamda.Compile();
_expressionReaderCache[typeOut] = creator;
}
return((Func <IDataRecord, o>)creator);
}
