WPF - 使用Int32.Parse

Question

在ComboBoxNotEmptyValidationRule類使用Int32.Parse後後的錯誤，我得到一個錯誤：

Input string was not in a correct format. 

當我添加到XAML：

<local:ComboBoxNotEmptyValidationRule x:Name="Number" ValidatesOnTargetUpdated="True"/> 

計劃是normaly運行，這walidation工作正常。在設計窗口我沒有任何內容，只有FormatException: Input string was not in a correct format.消息。當我在XAML中評論這一行時，一切都很好。

class ComboBoxNotEmptyValidationRule : ValidationRule 
    { 
     public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo) 
     { 
      int str = -1; 
       str = Int32.Parse(value as string); 
      if (str > 0) 
      { 
       if (str > 0) 
        return ValidationResult.ValidResult; 
      } 
      return new ValidationResult(false, "please fill required field"); 
     } 
    } 

Answer 1

你可以使用int32.TryParse

class ComboBoxNotEmptyValidationRule : ValidationRule 
{ 
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo) 
    { 
     int str; 
     if (Int32.TryParse(value as string, out str)) 
     { 
      if (str > 0) 
       return ValidationResult.ValidResult; 
     } 
     return new ValidationResult(false, "please fill required field"); 
    } 
} 

或者，你可以趕上FormatException，回到你的假驗證結果。

class ComboBoxNotEmptyValidationRule : ValidationRule 
{ 
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo) 
    { 
     int str = -1; 
     try 
     { 
      str = Int32.Parse(value as string); 
      if (str > 0) 
      { 
       if (str > 0) 
        return ValidationResult.ValidResult; 
      } 
      return new ValidationResult(false, "please fill required field"); 
     } 
     catch (FormatException) 
     { 
      return new ValidationResult(false, "please fill required field"); 
     } 
    } 
}