C#如何防止数据库中出现重复数据？

Question

当用户输入重复数据时，我如何防止“类(class)标题”在数据库中重复？

   SqlConnection cnn = new SqlConnection();
   SqlCommand cmd = new SqlCommand();
   SqlDataAdapter da = new SqlDataAdapter();
   SqlCommandBuilder cb = new SqlCommandBuilder(da);
   DataSet ds = new DataSet();
    cnn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Project1ConnectionString"].ConnectionString;
    cnn.Open();

    cmd.CommandText = "select * from  Lesson";
    cmd.Connection = cnn;

    da.SelectCommand = cmd;

    da.Fill(ds, "Lesson");


    DataRow drow = ds.Tables["Lesson"].NewRow();

    drow["TopicID"] = DropDownList1.Text;
    drow["LessonTitle"] = TextBox1.Text;
    drow["LessonDate"] = DateTime.Now;
    ds.Tables["Lesson"].Rows.Add(drow);
    da.Update(ds, "Lesson");

Answer 1

这种唯一性应该由数据库强制执行。向您的表添加唯一约束:

CREATE UNIQUE INDEX UK_Lesson_Title ON Lesson (Title)