Question

我正在做一个学校项目，在ExecuteNonQuery Sqlcommand之后遇到了这种情况

import React, { Component } from 'react'; // let's also import Component

// the clock's state has one field: The current time, based upon the
// JavaScript class Date
type ClockState = {
  time: Date
}

// Clock has no properties, but the current state is of type ClockState
// The generic parameters in the Component typing allow to pass props
// and state. Since we don't have props, we pass an empty object.
export class Clock extends Component<{}, ClockState> {

  // The tick function sets the current state. TypeScript will let us know
  // which ones we are allowed to set.
  tick() {
    this.setState({
      time: new Date()
    });
  }

  // Before the component mounts, we initialise our state
  componentWillMount() {
    this.tick();
  }

  // After the component did mount, we set the state each second.
  componentDidMount() {
    setInterval(() => this.tick(), 1000);
  }

  // render will know everything!
  render() {
    return <p>The current time is {this.state.time.toLocaleTimeString()}</p>
  }
}

如您所见，我在msgbox中应用了三元语句，条件是命令执行良好。我对其进行了测试，并执行了该程序，但由于>“ Update Success！Acctid 1”（acctid.text已连接）错误，程序崩溃了。字符串到整数，强制转换异常从字符串“ Update Success！Acctid 1”到类型“ Integer”的转换无效。

那是为什么？显然，返回必须是字符串，并且该语句中的任何内容都不应启动从字符串到整数的转换。首先是另一种方式，这是两个字符串的有效连接

Answer 1

“我在msgbox中应用了三元语句” 。嗯，不，你没有。您仅向MsgBox提供了三个参数，而与该函数的期望无关。 VB中的三元运算符为If，并且您的代码中没有If。如果要使用三元运算符，则需要使用一个：

MsgBox(If(c.ExecuteNonQuery > 0, "Update Success! Acctid " & acctid.Text, "Update Failed!"))

MSGBOX的字符串，混淆为强制转换为整数VB.net

1 个答案: