How to Convert This Foreach Code to Parallel.Foreach

How can I convert foreach code to Parallel.ForEach?

I'm not sure what you're looking for, but here's how you can accomplish it based on your query. Keep in mind that your logic inside the foreach block must be "paralleled-ready".

Paraller.foreach (archive.Entries,(pictureEntry)=>
               {
                            if (string.Equals(pictureEntry.Name, imageName, StringComparison.OrdinalIgnoreCase))
                            {
                                //for reading the image
                                byte[] buffer;
                                long length = pictureEntry.Length;
                                buffer = new byte[length];
                                pictureEntry.Open().Read(buffer, 0, (int)length);
                                myImage.Source = ImageSource.FromStream(() => new MemoryStream(buffer));

                            }
               });

You can refer official documentation also - [1]:https://docs.microsoft.com/en-us/dotnet/standard/parallel-programming/how-to-write-a-simple-parallel-foreach-loop?redirectedfrom=MSDN

How can I convert this foreach code to Parallel.ForEach?

string[] lines = File.ReadAllLines(txtProxyListPath.Text);
List<string> list_lines = new List<string>(lines);
Parallel.ForEach(list_lines, line =>
{
    //Your stuff
});

Convert foreach to Parallel.ForEach

I would use an overload of the Parallel.ForEach so your i parameter is provided by the foreach method:

Parallel.ForEach(DT.Rows.OfType<System.Data.DataRow>(), (DataRow row2, ParallelLoopState loopState, long i) =>
{
    try {
        bool check = (urlcheck(dataGridView.Rows[(int)i].Cells[2].Value.ToString()));
        if (check == true)
            ExecuteQuery("");
        else
            ExecuteQuery("");
    }
    catch{ }
});

For the OfType<> method you need to add using System.Linq to your using statements.

Now the index (i) is automaticly assigned by the method call so you don't have to worry about thread safety of i.

How to convert foreach to Parallel.Foreach in c#

This is because the foreach is converting the items in the ArrayList to string from an object. All the items in an ArrayList are object at compile time, and object doesn't have a method called StartsWith.

In this case:

foreach (string item in list)

item is converted into a string from object.

To do the same you will need to perform the conversion yourself e.g.

Parallel.ForEach(list.OfType<string>().ToArray(), item ....

Or .Cast<string> instead of OfType if you want to fail at runtime if there's a non-string instance in your list.

Alternatively use a generic list such as List<String> to avoid runtime casting.

Foreach into Parallel.Foreach c#

I am not sure what are you asking for but based on your question, here is how you can do that. Keep in mind that your logic inside must be "paralleled-ready".

Parallel.ForEach(storeCodesData, (storeData) => 
      {
      string[] storeDataSplit = storeData.Split(',');
      if (storeDataSplit[0] != "")
      {
          Store store1 = new Store { StoreCode = storeDataSplit[0], StoreLocation = storeDataSplit[1] };
          stores.Add(store1);
          storename.Add( storeDataSplit[1]);
      }
      PopulateListViewItems(storeDataSplit[0]);
      });

Parallel.ForEach loop is not working it skips some and double do others

Thanks to sedat-kapanoglu, I found the problem is really about thread safety. The solution was to change every List<T> to ConcurrentBag<T>.

For everyone, like me, The solution of "parallel not working with collections" is to change from System.Collections.Generic to System.Collections.Concurrent

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