string str = “Hello”+ “World”； 
console.WriteLine（str）；//输出 “HelloWorld”

string 【】 str1 = “Hello”； 

string 【】 str2 = “World”； 

string.Join（“/”,str1，str2）；//输出 “Hello/World”，以“/”作为分隔符进行连接

int IntStr = 100； 
string str = “Hello”； 
string.Concat（IntStr，str）；//输出 “100Hello”；

StringBuilder MyStringBuilder = new StringBuilder();
MyStringBuilder.Append(yy);
MyStringBuilder.Append(zz);
string yy = MyStringBuilder.ToString();

String book_type = this.DropDownList1.SelectedValue;
String bookname = this.book_name.Text.Trim();
String price = this.price.Text.Trim();
String write = this.writer.Text.Trim();
String kaiben = this.kaiben.Text.Trim();
String yinzhang = this.yingzhang.Text.Trim();
String k=this.DropDownList2.SelectedValue;
String zishu = this.text.Text.Trim();
zishu = zishu + k;
String version = this.version.Text.Trim();
String bookhao = this.bookhao.Text.Trim();
String yingshu = this.yingshu.Text.Trim();
String jiejie = this.jiejie.Text.Trim();
String fullname = this.FileUpload1.FileName;
Response.Write(fullname + "<br>");
String filepath = "";

String temp = String.Join("','", book_type, bookname, price, write, kaiben, yinzhang, zishu, version, bookhao,yingshu, filepath, jiejie);
String sql = "insert into 图书表(类型编号,图书名,价格,作者,开本,印张,字数,版次,书号,印数,图片,图书简介) values('"+temp+"')";