Configuring tasks.json for C/C++ debugging

tasks.json

// Available variables which can be used inside of strings.
// ${workspaceRoot}: the root folder of the team        
// ${file}: the current opened file                     
// ${fileBasename}: the current opened file's basename 
// ${fileDirname}: the current opened file's dirname    
// ${fileExtname}: the current opened file's extension  
// ${cwd}: the current working directory of the spawned process


{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "build",
            "type": "shell",
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "presentation": {
                "echo": true,
                "reveal": "always",
                "focus": false,
                "panel": "shared"
            },
            "windows": {
                "command": "g++",
                "args": [
                    "-ggdb",
                    "\"${file}\"",
                    "--std=c++11",
                    "-o",
                    "\"${fileDirname}\\${fileBasenameNoExtension}.exe\""
                ]
            }
        }
    ]
}

hello friend im having an error when i start debugging Could not find the task 'g++ build active file'
i know its my problem not your code but what would i do i dont have experience with JSON