c# JSON解析给出错误的系统。解析JSON数组时的ArgumentNullException

I'm trying to parse this JSON:

我正在解析JSON:

{"error":[],"result":{"XETHXXBT":{"a":["0.023769","64","64.000"],"b":["0.023756","42","42.000"],"c":["0.023756","1.21518360"],"v":["74038.22109284","130984.00945101"],"p":["0.023689","0.006974"],"t":[1272,2332],"l":["0.023440","0.023440"],"h":["0.024091","0.024669"],"o":"0.024084"}}}
{