又要麻烦各位了,正在学习《C# 入门经典(第4版)》中的C#委托,但是书中的一个例子我却无法编译class Program
{
delegate double ProcessDelegate(double param1, double param2);
static double Multiply(double param1, double param2)
{
return param1 * param2;
}
static double Divide(double param1, double param2)
{
return param1 / param2;
}
static void Main(string[] args)
{
ProcessDelegate process;
Console.WriteLine("Enter 2 numbers separated with a comma:");
string input = Console.ReadLine();
int commaPos = input.IndexOf(',');
double param1 = Convert.ToDouble(input.Substring(0, commaPos));
double param2 = Convert.ToDouble(input.Substring(commaPos + 1, input.Length - commaPos - 1));
Console.WriteLine("Enter M to multiply or D to divide;");
input = Console.ReadLine();
if (input == "M")
process = new ProcessDelegate(Multiply);
Console.WriteLine("Result: {0}", process(param1, param2));
Console.ReadKey();
}
}
编译的错误,提示我“使用了未赋值的局部变量“process”“
请问各位这是什么原因,书中并未写到委托之后需要赋值。
{
delegate double ProcessDelegate(double param1, double param2);
static double Multiply(double param1, double param2)
{
return param1 * param2;
}
static double Divide(double param1, double param2)
{
return param1 / param2;
}
static void Main(string[] args)
{
ProcessDelegate process;
Console.WriteLine("Enter 2 numbers separated with a comma:");
string input = Console.ReadLine();
int commaPos = input.IndexOf(',');
double param1 = Convert.ToDouble(input.Substring(0, commaPos));
double param2 = Convert.ToDouble(input.Substring(commaPos + 1, input.Length - commaPos - 1));
Console.WriteLine("Enter M to multiply or D to divide;");
input = Console.ReadLine();
if (input == "M")
process = new ProcessDelegate(Multiply);
Console.WriteLine("Result: {0}", process(param1, param2));
Console.ReadKey();
}
}
编译的错误,提示我“使用了未赋值的局部变量“process”“
请问各位这是什么原因,书中并未写到委托之后需要赋值。
这句可能没执行到吧
外面 执行不到
ProcessDelegate process= new ProcessDelegate(Divide);
process = new ProcessDelegate(Multiply);
else
process = new ProcessDelegate(Divide);
替换上面的if字段就ok了
谢谢楼上各位的提醒。