C# Foreach keep adding the same item to list

You are always accessing by index zero constantly. Options to correct:

1. If you use foreach use:

   foreach (var material in materialUsed)
   {
       var deliveryModel = new DeliveredTaskModel();
       deliveryModel.Info = material.SubPartCode;
       deliveryModel.Description = material.Description;
       deliveryModel.Qty = material.Qty;
       deliveredTaskModel.Add(deliveryModel);
   }
   

2. If you use by indexer change to for-loop:

   for(int i = 0; i < materialUsed.Count, i++)
   {
       var deliveryModel = new DeliveredTaskModel();
       deliveryModel.Info = materialUsed[i].SubPartCode;
       deliveryModel.Description = materialUsed[i].Description;
       deliveryModel.Qty = materialUsed[i].Qty;
       deliveredTaskModel.Add(deliveryModel);
   }
   

3. Then it will be nicer to user property initializer:

   foreach (var material in materialUsed)
   {
       deliveredTaskModel.Add(new DeliveredTaskModel
       {
           Info = material.SubPartCode,
           Description = material.Description,
           Qty = material.Qty
       });
   }
   

4. And then using linq you can achieve it with .Select

   var deliveredTaskModel = materialUsed.Select(material => new DeliveredTaskModel
       {
           Info = material.SubPartCode,
           Description = material.Description,
           Qty = material.Qty
       }).ToList();
   

I suggest you go with the last option :)

One last comment - your if statement (materialUsed.Count > 0) is redundant because if collection is empty it won't go into the loop

You are referencing the same fixed index in your loop:

deliveryModel.Info = materialUsed[0].SubPartCode;

You need to use the loop variable:

deliveryModel.Info = material.SubPartCode;

You should use the current item in each iteration of the foreach loop instead of referencing the list. Try this:

IList<DeliveredTaskModel> deliveredTaskModel = new List<DeliveredTaskModel>();

        if (materialUsed.Count > 0)
        {
            foreach (var material in materialUsed)
            {
                var deliveryModel = new DeliveredTaskModel();
                deliveryModel.Info = material .SubPartCode;
                deliveryModel.Description = material .Description;
                deliveryModel.Qty = material .Qty;
                deliveredTaskModel.Add(deliveryModel);
            }
        }