几种判断类型的方法

public static bool IsNumber(string expression)
public static bool IsInteger(string expression)
{
if(expression.Trim().Length == 0)
{
return false;
}
// leading - is ok
expression = expression.Trim();
int startIdx = 0;
if(expression.StartsWith("-"))
{
startIdx = 1;
}
for(int i=startIdx;i<expression.Length;i++)
{
if(!char.IsNumber(expression[i]))
{
return false;
}
}
return true;
}