按照以下方式尝试

try this in the Following way

 foreach (ListItem item in ListBox1.Items)
           {
               strc += item + ",";
           }


//You are taking string for ListBox items instead of list Item

像这样对您有用

Do it like that it should work for you

listBox1.Items.Cast<object>().Aggregate((item1, item2) => item1 + "," + item2).ToString();
</object>

在您的代码中，问题出在这里

In your code the problem is here

foreach (string itm in listBox1.Items)