The issue you’re experiencing is because NewRow is referencing the same object as CurRow. In C#, when you assign one object to another, they both reference the same memory location. To create a true copy of the object, you need to clone it. Since Fold_Trans is an Entity Framework entity, you can manually create a deep copy of the object.

Here’s an example of how you can create a copy of CurRow:

1. Create a method to clone your Fold_Trans object.
2. Use this method to create a new instance for NewRow.

Below is the modified code:

var CurRow = db.Fold_Trans.AsNoTracking().First(x => x.ID == Id);

List<Fold_Trans> LsFoldTrans = new List<Fold_Trans> { CurRow };

var OrgGmtrs = decimal.Parse(TxtOrgGMtrs.EditValue.ToString());
var TpMtrs = decimal.Parse(TxtTPGMtrs.EditValue.ToString());
var BalMtrs = OrgGmtrs - TpMtrs;

var OrgWt = decimal.Parse(TxtOrgWt.EditValue.ToString());
var OrgAvgWt = decimal.Parse(TxtOrgAvgWt.EditValue.ToString());
var TpWt = OrgAvgWt * TpMtrs;
var BalWt = OrgWt - TpWt;

// Clone the CurRow object to create a new instance for NewRow
var NewRow = CloneFoldTrans(CurRow);

CurRow.Gmtrs = BalMtrs;
CurRow.Weight = BalWt;

int ExCn = 1;

string NewPieceNo = CurRow.Piece + @$"-TP{ExCn}";
string NewMainPieceNo = CurRow.MainPiece + @$"-TP{ExCn}";

NewRow.Piece = NewPieceNo;
NewRow.MainPiece = NewMainPieceNo;
NewRow.Gmtrs = TpMtrs;
NewRow.Weight = TpWt;
NewRow.ID = 0;

LsFoldTrans.Add(NewRow);

db.Fold_Trans.AddUpdateOrDeleteCommRange(LsFoldTrans, x => x.ID == Id);
db.SaveChanges();

Fold_Trans CloneFoldTrans(Fold_Trans source)
{
    return new Fold_Trans
    {
        // Copy all the properties from source to new instance
        Piece = source.Piece,
        MainPiece = source.MainPiece,
        Gmtrs = source.Gmtrs,
        Weight = source.Weight,
        // Copy other properties as needed
        // Ensure not to copy the ID if you want a new row in the database
        // Exclude any properties that should not be copied
        // You may also want to include any navigation properties if needed
    };
}

In this code:

• CloneFoldTrans method creates a new instance of Fold_Trans and copies
  the values from the source object.
• NewRow is created by cloning CurRow to ensure they do not reference
  the same object.
• CurRow and NewRow can then be independently modified without
  affecting each other.