YamlDotNet深度合并两个YAML文件：库内是否有简便实现方式？

Does YamlDotNet have a built-in way to deep merge two YAML files? #

Short answer—no, YamlDotNet doesn’t include a native API for deep merging two separate YAML files out of the box.

You mentioned the question about the merge key (<<), and that’s a common point of confusion. That feature is part of the YAML specification itself, not a YamlDotNet-specific tool for cross-file merging. It lets you reuse and merge structures within a single YAML file using anchors and references, like this:

default_config: &default
  timeout: 30
  retries: 2

production_config:
  <<: *default
  retries: 5
  endpoint: "prod.example.com"

YamlDotNet will parse this into a single merged object where production_config inherits timeout:30 and overrides retries to 5. But this only works if you structure your YAML files to use this syntax upfront—it doesn’t let you take two unrelated YAML files and merge their contents automatically.

Implementing Deep Merge for Two YAML Files #

To merge two independent YAML files deeply, you’ll need to:

1. Deserialize both files into a flexible data structure (like Dictionary<object, object>)
2. Write a recursive function to merge the structures
3. Serialize the merged result back to YAML

Here’s a complete example:

Step 1: Deserialize the YAML Files #

using YamlDotNet.Serialization;
using YamlDotNet.Serialization.NamingConventions;
using System.IO;
using System.Collections.Generic;

// Set up the deserializer (adjust naming convention to match your YAML style)
var deserializer = new DeserializerBuilder()
    .WithNamingConvention(CamelCaseNamingConvention.Instance)
    .Build();

// Load and deserialize first YAML file
using var file1Reader = new StreamReader("config1.yaml");
var yamlData1 = deserializer.Deserialize<Dictionary<object, object>>(file1Reader);

// Load and deserialize second YAML file
using var file2Reader = new StreamReader("config2.yaml");
var yamlData2 = deserializer.Deserialize<Dictionary<object, object>>(file2Reader);

Step 2: Recursive Deep Merge Function #

This function will merge yamlData2 into yamlData1, with these rules:

• Add new keys from yamlData2 to yamlData1
• Recursively merge nested dictionaries
• Append items from yamlData2 lists to yamlData1 lists (adjust this logic if you need to replace or deduplicate)
• Override existing non-dictionary/non-list values with yamlData2 values

void DeepMergeDictionaries(Dictionary<object, object> target, Dictionary<object, object> source)
{
    foreach (var (key, sourceValue) in source)
    {
        if (!target.TryGetValue(key, out var targetValue))
        {
            // Key doesn't exist in target—add it
            target[key] = sourceValue;
            continue;
        }

        // Both values are dictionaries: recurse
        if (targetValue is Dictionary<object, object> targetDict && sourceValue is Dictionary<object, object> sourceDict)
        {
            DeepMergeDictionaries(targetDict, sourceDict);
        }
        // Both values are lists: append source items to target
        else if (targetValue is IList targetList && sourceValue is IList sourceList)
        {
            foreach (var item in sourceList)
            {
                targetList.Add(item);
            }
        }
        // For all other types: override target value with source
        else
        {
            target[key] = sourceValue;
        }
    }
}

// Run the merge
DeepMergeDictionaries(yamlData1, yamlData2);

Step 3: Serialize the Merged Result #

var serializer = new SerializerBuilder()
    .WithNamingConvention(CamelCaseNamingConvention.Instance)
    .Build();

using var mergedFileWriter = new StreamWriter("merged_config.yaml");
serializer.Serialize(mergedFileWriter, yamlData1);

Customizing the Merge Logic #

You can tweak the DeepMergeDictionaries function to fit your needs:

• Change list handling to replace instead of append
• Add deduplication logic for list items
• Skip certain keys from being overwritten
• Handle specific value types (like numbers, booleans) with custom rules

内容的提问来源于stack exchange，提问作者Dragouf