Question

    private void fillProduct() {

    SqlConnection conn = new SqlConnection("Data Source=STATION21\\SQLEXPRESS;Initial Catalog=mydb;Integrated Security=true");
    conn.Open();

    string query = "Select prodID from product";

    SqlCommand cmd = new SqlCommand(query, conn);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    da.Fill(dt);

    if (dt.Rows.Count > 0) {
        cmbPCode.DataSource = dt;
        cmbPCode.DisplayMember = "prodID";
        cmbPCode.ValueMember = "prodID";
    }


    private void cmbPCode_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("Data Source=STATION21\\SQLEXPRESS;Initial Catalog=mydb;Integrated Security=true");
        con.Open();

        string query = "Select * from product where prodID = '"+cmbPCode.Text+"'".ToString();

        SqlCommand cmd = new SqlCommand(query, con);

        SqlDataReader dr = cmd.ExecuteReader();

        if (dr.Read()) {
            tbdc.Text = dr["prodDescription"].ToString();
        }
    }

我无法根据所选索引从数据库中获取我的项目时出现此错误

转换varchar值时转换失败＆＃39; System.Data.DataRowView＆＃39;到数据类型int

有人可以帮助我如何将SqlDataReader转换为String。因为我注意到当我使用varchar / string数据类型检索列时，我没有这种错误但是如果我检索到具有int数据类型的列，则会出现此错误。

Answer 1

替换它：

string query = "Select * from product where prodID = '"+cmbPCode.Text+
                                                                 "'".ToString();

有了这个：

string query = "Select * from product where prodID = "+cmbPCode.Text;

建议：您的查询对SQL注入是开放的我建议您使用参数化查询来避免它们。

使用参数化查询：

 string query = "Select * from product where prodID = @ID";
 SqlCommand cmd = new SqlCommand(query, con);
 cmd.Parameters.AddWithValue("@ID",cmbPCode.Text);

使用数据库中的选定项填充文本框

1 个答案: