直接贴代码了，有问题私信
static void Main(string[] args)
{
try
{
string filePath = @"C:\test\原始单据.txt";
string result = "";
using (StreamReader sr = new StreamReader(filePath, Encoding.Default))
{
string fileContent = string.Empty;
string strLine = string.Empty;
while (strLine != null)
{
strLine = sr.ReadLine();
if (strLine != null)
{
if (strLine.Contains("单据号 :"))
{
string djh = strLine.Substring(strLine.IndexOf("单据号 :") + 5);
result += djh + " ";
}
else if (strLine.Contains("总金额 :"))
{
string je = strLine.Substring(strLine.IndexOf("总金额 :") + 5);
result += je + "\r\n";
}
}
}

            }
            Console.WriteLine(result);
            Console.Read();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        Console.Read();
    }