How to set both key and value pair as variable

Describe the bug
I want to write a generic storage handler into an json file. Key and value are variables

void setSetting ( CString key, Integer value)
{
Json::Value data;
data[key] = value;
///write json
}

Result in VS2022 Compiler:
Severity Code Description Project File Line Suppression State
Error C2678 binary '[': no operator found which takes a left-hand operand of type 'Json::Value' (or there is no acceptable conversion) Editor ConfigJson.cpp 61

To Reproduce
Steps to reproduce the behavior:

1. Use a variable as key instead of a static String

Expected behavior
should write the key/pair pair

Desktop (please complete the following information):

• OS: Win10
• Visual Studio 2022

Start at ConfigJson.cpp line 61 and inspect the Json::Value operator[] overloads used with the variable key and value types. Reproduce the C2678 error in Visual Studio 2022, then confirm that the generic storage handler compiles and writes the expected key/value pair to the JSON file.