退出不插入其他插入

Question

我已經開始學習asp.net了。我正在使用VS 2013 Express for C＃。 如何使一個如果情況下檢查一個重複的值，如果這個值是存在的，那麼我得到一個紅色的總結關於它，不能插入到數據庫插入到數據庫，也使用更新按鈕。

你能幫忙嗎？

SqlConnection con = new SqlConnection(@"Data Source=TSS\SQLEXPRESS;Initial Catalog=DB;Integrated Security=True"); 

protected void Add(object sender, EventArgs e) 
{ 
    var vardas = GridView1.FooterRow.FindControl("txtname") as TextBox; 
    var pavarde = GridView1.FooterRow.FindControl("txtlastname") as TextBox; 
    var pozymis = GridView1.FooterRow.FindControl("DropDownList2") as DropDownList; 

    SqlCommand comm = new SqlCommand(); 
    comm.CommandText = "insert into asmenys (name,lastname, status) values(@name,@lastname, @status)"; 
    comm.Connection = con; 

    comm.Parameters.AddWithValue("@name", name.Text); 
    comm.Parameters.AddWithValue("@lastname", lastname.Text); 
    comm.Parameters.AddWithValue("@status", status![enter image description here][1].Text); 

    con.Open(); 
    comm.ExecuteNonQuery(); 
    con.Close(); 

    DataBind(); 
} 

Answer 1

當你說是否存在一個值，哪些領域應該不會有重複？這些是你必須編寫一個select語句來檢查它們是否先存在的字段。

例

protected void Add(object sender, EventArgs e) 
{ 
    var vardas = GridView1.FooterRow.FindControl("txtname") as TextBox; 
    var pavarde = GridView1.FooterRow.FindControl("txtlastname") as TextBox; 
    var pozymis = GridView1.FooterRow.FindControl("DropDownList2") as DropDownList; 

    SqlCommand comm = new SqlCommand(); 

    comm.CommandText = "select lastname from asmenys where lastname = @lastname"; 
    comm.Parameters.AddWithValue("@lastname", lastname.Text); 

    SqlDataReader reader = comm.ExecuteReader(); 

    if (reader.HasRows) 
    { 
     Console.WriteLine("Values exist"); 
    } 
    else 
    { 
     comm.CommandText = "insert into asmenys (name,lastname, status) values(@name,@lastname, @status)"; 
     comm.Connection = con; 

     comm.Parameters.AddWithValue("@name", name.Text); 
     comm.Parameters.AddWithValue("@lastname", lastname.Text); 
     comm.Parameters.AddWithValue("@status", status![enter image description here][1].Text); 

     con.Open(); 
     comm.ExecuteNonQuery(); 
     con.Close(); 

     DataBind(); 
    } 
}