如何合并重复string对应的int值为带int列表的对象集合

Hey there! To achieve what you want—grouping entries by the string value and combining their integers into a list—you can use LINQ's grouping capabilities paired with a clear data structure to hold the merged results. Here's how to do it step by step:

Step 1: Define a Class for Merged Entries (Recommended) #

First, create a concrete class to represent your merged objects. This makes working with the data much easier later on, compared to using anonymous types:

public class MergedEntry
{
    public string Pars { get; set; }
    public List<int> Ids { get; set; } = new List<int>(); // Initialize with empty list by default
}

Step 2: Merge Existing Individual Entries #

If you already have a collection of individual (string, int) entries (either in your result list or another source), you can group them and convert to merged entries using LINQ:

Example Source Data #

Let's say you have a list of individual items (this could be extracted from your existing result list if needed):

// Example: Your existing individual entries (replace with your actual data source)
var individualEntries = new List<(string Pars, int Id)>
{
    ("xxx", 1),
    ("xxx", 2),
    ("yyy", 3),
    ("xxx", 4),
    ("zzz", 5)
};

Group and Merge #

Use GroupBy to cluster entries by the Pars string, then create MergedEntry objects for each group:

var mergedEntries = individualEntries
    .GroupBy(entry => entry.Pars)
    .Select(group => new MergedEntry
    {
        Pars = group.Key,
        Ids = group.Select(entry => entry.Id).ToList()
    })
    .ToList();

// Assign to your result list (cast to object if you need to keep List<object>)
List<object> result = mergedEntries.Cast<object>().ToList();

After this, result will contain:

• { Pars = "xxx", Ids = [1,2,4] }
• { Pars = "yyy", Ids = [3] }
• { Pars = "zzz", Ids = [5] }

Step 3: Incremental Addition (Adding Items One by One) #

If you're adding items to result incrementally (instead of processing a full list at once), check for existing entries before adding:

// Suppose you're adding a new entry: string newPars = "xxx"; int newId = 6;

// Check if the Pars already exists in result
var existingEntry = result.OfType<MergedEntry>().FirstOrDefault(e => e.Pars == newPars);

if (existingEntry != null)
{
    // Add the new Id to the existing list
    existingEntry.Ids.Add(newId);
}
else
{
    // Create a new MergedEntry and add it to result
    result.Add(new MergedEntry { Pars = newPars, Ids = new List<int> { newId } });
}

Notes #

• Avoid Anonymous Types: While you could use anonymous objects for merging, using a concrete class like MergedEntry makes it easier to access properties later (you can't easily cast anonymous types back to their original structure).
• Handling Existing result Data: If your result list already contains individual (string, int) objects, first extract them using result.OfType<YourIndividualClass>().ToList() (replace YourIndividualClass with the class you used for single entries) before grouping.

内容的提问来源于stack exchange，提问作者Leo Messi