注册信息填入过后无法成功找到已填入信息，也就是说插入表失败

Question

string strSQL = "insert into user values ";
strCon += "('" + this.username_txt.Text + "','" + this.password_txt.Text + "','" + this.email_txt.Text + "','" + this.address_txt.Text + "',";
strSQL += "' " + this.familyname_txt.Text + "','" + this.givenname_txt.Text + "','" + this.idcard_txt.Text + "')";
请问这个插入语言有问题吗？注册过后找不到注册的信息，也就是说没能成功插入到user表中。
整个代码如下：
string strCon = WebConfigurationManager.ConnectionStrings["RAINBOWConnectionString"].ConnectionString;
SqlConnection sql = new SqlConnection();
sql.ConnectionString = strCon;
sql.Open();
SqlCommand cmd = new SqlCommand("select * from [user] where username='" + this.username_txt.Text + "'", sql);
SqlCommand cmd2 = new SqlCommand("select * from [user] where email='" + this.email_txt.Text + "'", sql);
string strSQL = "insert into user values ";
strCon += "('" + this.username_txt.Text + "','" + this.password_txt.Text + "','" + this.email_txt.Text + "','" + this.address_txt.Text + "',";
strSQL += "' " + this.familyname_txt.Text + "','" + this.givenname_txt.Text + "','" + this.idcard_txt.Text + "')";

    SqlCommand cmd3 = new SqlCommand(strSQL, sql);


    SqlDataReader dr = cmd.ExecuteReader();
    if (dr.Read())
    {
        this.Label1.Visible = true;
        dr = cmd2.ExecuteReader();
        if (dr.Read())
        {
            this.Label2.Visible = true;
            sql.Close();
        }
    }
    else
    {
        this.Label1.Visible = false;
        this.Label2.Visible = false;

        Server.Transfer("~/前台/Login.aspx");
    }
    sql.Close();

Answer 1

cmd3 .ExecuteNonQuery();