Note on using foreach in dictionary

Recently Program Performs performance optimization and uses dictionary during the optimization process. In When the data in is written to the database, the following error occurs:
Collection was modified; enumeration operation may not execute.

Code Similar to this: Dictionary < Int , Int > _ Dictionary =   New Dictionary < Int , In > ();
// Adding data operation omitted
Foreach (Keyvaluepair < Int , Int > Item In _ Dictionary)
{
}

When foreach is executed, other threads Add _ dictionary, which changes the data in _ dictionary and generates the preceding exception information.

So what will generate such exception information?
The actual code executed by foreach is:

Dictionary < Int , Int > . Enumerator = _ Dictionary. getenumerator ();
Try
{
While (Enumerator. movenext ())
{

}
}
Finally
{
Idisposable d = Enumerator As Idisposable;
If (D ! =   Null ) D. Dispose ();
}

View dictionary using reflector . enumerator. movenext () Source Code , we will find the code at the beginning: If ( This . version ! = This . dictionary. version)
{< br> throwhelper. throwinvalidoperationexception (exceptionresource. invalidoperation_enumfailedversion);
}

The exception occurs here because the version of the dictionary is changed during the add operation. You can view the source code of insert (tkey, tvalue, bool add.
I think dictionary <tkey, tvalue> should provide a method to set whether to perform version check in movenext, because sometimes in foreach operations, it may not care whether the data in the dictionary is modified, I have encountered this situation. Due to this problem, foreach cannot be used, but only other methods can be used to traverse data in dictionary <tkey, tvalue>.
The method I use is:

Dictionary < Int , Int > _ Dictionary =   New Dictionary < Int , In > ();
// Adding data operation omitted
Int [] Dataarray =   New   Int [_ Dictionary. Values. Count];
_ Dictionary. Values. copyto (evcarray, 0 )
For ( Int I =   0 ; I < Dataarray. length; I ++ )
{
}