How to change the value of a StringBuilder Parsing through JArray

Question

I have struggled to finish this task, please if anyone can give me a hint I would be so thankful.

My main task is to get data from database using (FOR JSON AUTO) which is working :)

select filed1, field2, field3 from table FOR JSON AUTO;

And then after connecting to Data base I use the StringBuilder() to build a Json Array of objects which is working :)

var jsonResult = new StringBuilder();
if(!r.HasRows)
{
   jsonResult.Append("[]");
}
else
{
    while(r.Read())
    {
       jsonResult.Append(r.GetValue(0).ToString());
    }
    // JArray array = JArray...
}

After that I am trying to change the value of filed1 for each object inside the Json Array

JArray array = JArray.Parse(jsonResult.ToString());

foreach (JObject obj in array.Children<JObject>())
{
   foreach (JProperty singleProp in obj.Properties())
   {
      string name = singleProp.Name;
      string value = singleProp.Value.ToString();
      if(name.ToString() == "field1")
      { 
         Int64 newID = 1234;
         value = newID.ToString();                            
      }                      
   }
}

This is working but My BIG QUESTION is how can I get it changed inside the jsonResult?

If you are creating the SQL query, why not also create a matching class object, deserialise the json into it, change the value, and serialise it again. — Neil
– Neil, Commented Feb 10, 2020 at 16:27
@Neil I am new to asp.net and sql, any more clarifications please? — hadi boukdir
– hadi boukdir, Commented Feb 10, 2020 at 16:34
Can you please edit your question to share a sample of the intermediate jsonResult.ToString() string -- i.e. a minimal reproducible example? And what is r.GetValue(0).ToString() returning? Is it already a JSON string? Because it's hard to see how your while loop would result in a valid JSON string. — dbc
– dbc, Commented Feb 10, 2020 at 17:04
In the absence of a minimal reproducible example this looks to be a duplicate of How do you Add or Update a JProperty Value in a JObject or How to update a property of a JSON object using NewtonSoft. — dbc
– dbc, Commented Feb 10, 2020 at 18:41
I think you dont need to convert the jsonResult to JArray. You can use r["field1"].ToString() == "1234" — alex
– alex, Commented Feb 10, 2020 at 20:43

Dharman · Accepted Answer · 2021-07-20 04:55:12Z

You simply have to replace the value that you want to update. Since StringBuilder has a .Replace inbuilt method, you can implement that method.

 `JArray arr = JArray.Parse(jsonResult.ToString());
 foreach (JObject obj in arr.Children<JObject>())
  {
      foreach(JProperty singleProp in obj.Properties())
      {
        string name = singleProp.Name;
        string value = singleProp.Value.ToString();
                    
        if (name.ToString().Equals("field1")) //good practice
        {
          Int64 newID = 1234;
          jsonResult.Replace(value, newID.ToString());//replacing old value with new value and directly updates jsonResult
        }

      //not necesssary, explanation is given below
        var jsonElement = JsonSerializer.Deserialize<JsonElement>(jsonResult.ToString());
         result = JsonSerializer.Serialize(jsonElement, options);
       }
   }`

And for better formatting, I used JsonSerializer so that your output will look like json object rather than whole string without any lines.

` var options = new JsonSerializerOptions()
                {
                    WriteIndented = true
                };
  var result = ""
  while loop{
     jsonResult.Append(r.GetValue(0).ToString());
     (Above code)
  }
`

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