使用c＃visual studio避免空白并在文本框中显示错误消息

Question

我有一个TextBox和保存按钮。 Textbox仅设置为数字，必须输入至少3个数字和最多4个数字。我需要这样做，以便在框中输入所有或什至一个空格时，我需要显示一条错误消息。在当前代码中，我设置了输入2位数字后将显示的错误消息。但是mtuValue是int属性。我需要一条if语句来避免并显示whitespace。代码如下。此当前代码适用于目前设置的任何内容。因此，我需要的是whitespace的if语句。提前非常感谢。

private ICommand MTUsavecommand_;
public ICommand MTUsavecommand
{
    get
    {
        if (null == MTUsavecommand_)
        {
            MTUsavecommand_ = new RelayCommand(o =>
            {
                if (mtuValue < 100)
                {
                    MtuMsg = "MTU value should be atleast 3 digits.";
                    MtuMsgVisibility = Visibility.Visible;
                }
                else
                {
                    Mouse.OverrideCursor = Cursors.Wait;
                    RouteManager?.DoMTU();
                    Mouse.OverrideCursor = null;
                    MtuMsg = "MTU saved successfully. Service will be restarted.";
                    MtuMsgVisibility = Visibility.Visible;
                }
            });
        }
        return MTUsavecommand_;
    }
}

public int mtuValue
{
    get { return Configuration.MTU; }
    set
    {
        if (Configuration.MTU != value)
        {
            Configuration.MTU = value;
            OnPropertyChanged();
        }
    }
}

Answer 1

如果您的项目是Winforms，则可以通过TextChanged事件检查TextBox中的数字是否满足要求。您可以使用控件errorProvider显示错误提示。

public Form1()
{
    InitializeComponent();
    // Set the blinking style: The error icon has been displayed, and blinks when it is still wrong to assign a new value to the control.
    errorProvider.BlinkStyle = ErrorBlinkStyle.BlinkIfDifferentError;
    // Set the distance of the error icon from the control
    errorProvider.SetIconPadding(this.textBox, 5);
}

private void textBox_TextChanged(object sender, EventArgs e)
{
    // Use TryParse method to check the format of digit (a properly formatted number should not contain spaces)
    int number;
    bool success = Int32.TryParse(textBox.Text, out number);
    string temp = textBox.Text.Trim();
    if (success && temp.Length == textBox.Text.Length) // Check for spaces at the beginning and end
    {
        // Check the number of digits
        if (textBox.Text.Length < 3 || textBox.Text.Length > 4)
            errorProvider.SetError(this.textBox, "Please input 3 or 4 digits");
        else
            errorProvider.SetError(this.textBox, "");
    }
    else // Wrong format
    {
        errorProvider.SetError(this.textBox, "Please input digit in right format");
    }
}