[{"id":"840f0737-df1d-47ae-bb0a-359b01fe0608","tags":[{"product":null,"links":null,"id":"adf72f47-7f61-4239-8392-b9bcc127fa80","name":"\u65B0\u589E","color":"green","productId":"0995490e-43fc-4d6e-bc8d-8e66f38b0c63"}]},{"id":"d5d9cdef-8854-4505-89be-a2bbc3cb4482","tags":[{"product":null,"links":null,"id":"adf72f47-7f61-4239-8392-b9bcc127fa80","name":"\u65B0\u589E","color":"green","productId":"0995490e-43fc-4d6e-bc8d-8e66f38b0c63"}]},{"id":"3dc3dd55-35b0-4d23-bf62-47bc3650e4ee","tags":[{"product":null,"links":null,"id":"adf72f47-7f61-4239-8392-b9bcc127fa80","name":"\u65B0\u589E","color":"green","productId":"0995490e-43fc-4d6e-bc8d-8e66f38b0c63"}]},{"id":"80d84fbc-d0f8-4e4a-947f-e3e4de9b49b2","tags":[{"product":null,"links":null,"id":"adf72f47-7f61-4239-8392-b9bcc127fa80","name":"\u65B0\u589E","color":"green","productId":"0995490e-43fc-4d6e-bc8d-8e66f38b0c63"}]},{"id":"9152b7ca-0186-4fe3-a26f-5a05f322db07","tags":[{"product":null,"links":null,"id":"adf72f47-7f61-4239-8392-b9bcc127fa80","name":"\u65B0\u589E","color":"green","productId":"0995490e-43fc-4d6e-bc8d-8e66f38b0c63"}]}]
IsNothing 函数用于判断一个参数是否是一个空引用指针对象。
比如，我们可以使用 IsNothing 函数来判断报表是否有参数值输入，然后配合IIF函数来实现如下效果：
如果未输入参数，报表内容则显示“未输入参数值”
如果输入了参数，报表内容则显示出参数的值。
1. 新建报表，并为报表定义一个可忽略的参数p1。
2. 在报表中添加一个文本框组件，并为文本框内添加表达式 {IIF(IsNothing(@p1), "未输入参数值", @p1)}。
3. 预览报表，查看效果。默认不需要输入参数，报表内容呈现“ 未输入参数值 ”；当输入参数值时，报表内容呈现参数的数值。
