protected void Button1_Click(object sender, EventArgs e)
        {
            //int X = Convert.ToInt32(Request.QueryString["tablename"]);
            int countjieguo = tongjibiao();
            int X = countjieguo - 2;             //要减去系统必须的3个表
            
            bool isexistbiao = isexist("table"+X.ToString());
            if (isexistbiao == false)
            {
                string sqlstr = "create table table'" + X + "' (id int identity not null,title nvarchar(100),username nvarchar(100),time datetime,content ntext,class nvarchar(100))";
                sqlEx(sqlstr);
               //string strupdate = "insert into table'" + X.ToString() + "' (title,username,time,content) values ('" + TextBox4.Text.ToString() + "' , " + "' 1 '" + " ,'" + DateTime.Now + "', '" + TextBox1.Text.ToString() + "')";
               //sqlEx(strupdate);
                MessageBox.Show("发帖成功！");
            }
            else
            {
                MessageBox.Show("发帖失败，请重试！");
            }

         }

string sqlstr = "create table table'" + X + "' (id int identity not null,title nvarchar(100),username nvarchar(100),time datetime,content ntext,class nvarchar(100))";
--这一句中创建表 create table table'是不合法的

------解决方案--------------------
"create table table" + X + "
没有table'7'这样的名字。
  去掉引号要么
"create table [table'" + X + "']..