c# – 如何限制字符串不超过一定长度？

参见英文答案 > How do I truncate a .NET string?25个
我试过以下：

var Title = LongTitle.Substring(0,20)

如果LongTitle的长度小于20,那么它可以工作,但是如果将字符串限制在最多20个字符,但是如果它们仅仅是例如5个字符长则不能得到错误.

解决方法

确保长度不会超过LongTitle(跳过空检查)：

int maxLength = Math.Min(LongTitle.Length,20);
string title = LongTitle.Substring(0,maxLength);

这可以变成扩展方法：

public static class StringExtensions
{

    /// <summary>
    /// Truncates string so that it is no longer than the specified number of characters.
    /// </summary>
    /// <param name="str">String to truncate.</param>
    /// <param name="length">Maximum string length.</param>
    /// <returns>Original string or a truncated one if the original was too long.</returns>
    public static string Truncate(this string str,int length)
    {
        if(length < 0)
        {
            throw new ArgumentOutOfRangeException("length","Length must be >= 0");
        }

        if (str == null)
        {
            return null;
        }

        int maxLength = Math.Min(str.Length,length);
        return str.Substring(0,maxLength);
    }
}

哪个可以用作：

string title = LongTitle.Truncate(20);