如何将自定义异常放入 Try-Catch-Finally 但在 Winforms 中同时使用 If 条件？答案

【问题标题】：How to put Custom Exceptions into Try-Catch-Finally but with If condition at the same time in winforms?如何将自定义异常放入 Try-Catch-Finally 但在 Winforms 中同时使用 If 条件？
【发布时间】：2020-12-13 05:15:14
【问题描述】：

我做了三个自定义例外。对于产品名称、数量和价格，但是当我尝试将其包含在尝试中时，它不会显示出来。我只需要异常工作，然后让它显示在控制台或消息框中。

原来是这样的：

 public string Product_Name(string name) {
if (!Regex.IsMatch(name, @"^[a-zA-Z]+$"))
   //Exception here
return name;
}
public int Quantity(string qty) {
if (!Regex.IsMatch(qty, @"^[0-9]"))
  //Exception here
return Convert.ToInt32(qty);
}

public double SellingPrice(string price)
{
if (!Regex.IsMatch(price.ToString(), @"^(\d*\.)?\d+$"))
   //Exception here
return Convert.ToDouble(price);
}

这是我尝试过的：

  public string Product_Name (string name)
    {
        if (!Regex.IsMatch(name, @"^[a-zA-Z]+$"))

            try
            {
                name = txtProductName.Text;
            }
            catch (Exception StringFormattException)
            {
                Console.WriteLine("Error info:" + StringFormattException.InnerException);
            }
            finally
            {
                Console.WriteLine("Executed.");
            }


        return name;
    }

另外两个也一样。

这是我放置自定义异常的类：

 class ProductClass
{
    private int _Quantity;
    private double _SellingPrice;
    private string _ProductName, _Category, _ManufacturingDate, _ExpirationDate, _Description;

    public ProductClass(string ProductName, string Category, string MfgDate, string ExpDate, double Price, int Quantity, string Description)
    {
        this._Quantity = Quantity;
        this._SellingPrice = Price;
        this._ProductName = ProductName;
        this._Category = Category;
        this._ManufacturingDate = MfgDate;
        this._ExpirationDate = ExpDate;
        this._Description = Description;
    }

    public string productName
    {
        get
        {
            return this._ProductName;
        }
        set
        {
            this._ProductName = value;
        }
    }

    public string Category
    {
        get
        {
            return this._Category;
        }
        set
        {
            this._Category = value;
        }
    }

    public string manufacturingDate
    {
        get
        {
            return this._ManufacturingDate;
        }
        set
        {
            this._ManufacturingDate = value;
        }
    }

    public string expirationDate
    {
        get
        {
            return this._ExpirationDate;
        }
        set
        {
            this._ExpirationDate = value;
        }
    }

    public string description
    {
        get
        {
            return this._Description;
        }
        set
        {
            this._Description = value;
        }
    }

    public int quantity
    {
        get
        {
            return this._Quantity;
        }
        set
        {
            this._Quantity = value;
        }
    }

    public double sellingPrice
    {
        get
        {
            return this._SellingPrice;
        }
        set
        {
            this._SellingPrice = value;
        }


    }



    class NumberFormattException : Exception 
    { 
        public NumberFormattException(string Quantity) : base(Quantity) { } 
    }

    class StringFormattException : Exception
    {
        public StringFormattException(string Product_Name) : base(Product_Name) { }
    }
    class CurrencyFormatException : Exception
    {
        public CurrencyFormatException( string SellingPrice) : base(SellingPrice) { }
    }



}

【问题讨论】：

阅读异常情况。单个try 可以有多个关联的catch 块，每个块都有不同的异常类型。例如，如果您有 3 种可能抛出的异常类型（Ex1、Ex2 和 Ex3），您可以编写 try { SomeCode(); } catch (Ex1 e1) { CatchCode1(e1); } catch (Ex2 e2) { CatchCode2(e2); } catch (Ex3 e3) { CatchCode(e3); } finally { FinCode(); }。注意catch语句的格式，异常规范就像一个方法参数规范：catch(ExceptionType exVariable)。如果你有多个 catch 块，第一个匹配的获胜

标签： c# winforms exception try-catch-finally

【解决方案1】：

你需要写：

catch (StringFormattException ex)
{
    string msg = ex.Message;
    if ( ex.InnerException != null )
      msg += $" ({ex.InnerException.Message})";
    // Also you can do a loop to get all inners
    Console.WriteLine("String format error: " + msg);
}

因为如果你写：

catch (Exception StringFormattException)
{
  ...
}

这里Exception 是一个类型，StringFormattException 是异常上下文实例的变量名称，如下所示：

string StringFormattException = "test";

try-catch (C# Reference)

【讨论】：