c#学生成绩转换问题 c#错误 1 运算符“/”无法应用于“System.Windows.Forms.TextBox”和“int”类型

程序如下：
private void button1_Click(object sender, EventArgs e)
{
// decimal tBox1;



int soperate =Convert.ToInt32(tBox1/10);

// soperate =Convert.ToInt32( button1.Text);

//tBox2.Text = Convert.ToString(tBox2);

switch (soperate)
{
case 10: tBox2.Text = "优秀";
break;

case 9: tBox2.Text = "优秀";
break;

case 8: tBox2.Text = "良好";
break;

case 7: tBox2.Text = "中等";
break;

case 6: tBox2.Text = "及格";
break;

default: tBox2.Text = "不及格";
break;

}

}

tBox1 是什么？是个textbox的ID？怎么当成变量用了
int soperate =Convert.ToInt32(Convert.ToInt32(tBox1.Text)/10);

当然不能隐式转换了 textbox里面本来是string型的 string和int只能强转 所以改你划红线那句 user.registernum=integer.parseint(textbox1.text);