47

我有一个包含 3 列的数据库表firstname，Lastname并且age. 在我的 C# Windows 应用程序中，我有 3 个名为的文本框textbox1......我使用以下代码连接到我的 SQL Server：

SqlConnection con = new SqlConnection("Data Source = .;
                                       Initial Catalog = domain;
                                       Integrated Security = True");
con.Open();
SqlCommand cmd = new SqlCommand("Select * from tablename", con);

我想从我的数据库中获取值；如果我给它一个值，textbox1它必须匹配数据库中的值并将其他详细信息检索到相应的文本框。

我尝试了这种方法，但它不起作用：

cmd.CommandText = "select * from tablename where firstname = '" + textBox1.Text + "' ";

如何将所有其他值检索到文本框？

4

6 回答 6

92 
 public Person SomeMethod(string fName)
        {
            var con = ConfigurationManager.ConnectionStrings["Yourconnection"].ToString();

            Person matchingPerson = new Person();
            using (SqlConnection myConnection = new SqlConnection(con))
            {
                string oString = "Select * from Employees where FirstName=@fName";
                SqlCommand oCmd = new SqlCommand(oString, myConnection);
                oCmd.Parameters.AddWithValue("@Fname", fName);           
                myConnection.Open();
                using (SqlDataReader oReader = oCmd.ExecuteReader())
                {
                    while (oReader.Read())
                    {    
                        matchingPerson.firstName = oReader["FirstName"].ToString();
                        matchingPerson.lastName = oReader["LastName"].ToString();                       
                    }

                    myConnection.Close();
                }               
            }
            return matchingPerson;
        }

这里有几件事需要注意：我使用了参数化查询，这使您的代码更安全。使用部件制作 select 语句的方式使您面临"where x = "+ Textbox.Text +""SQL 注入。

我已将其更改为：

  "Select * from Employees where FirstName=@fName"
  oCmd.Parameters.AddWithValue("@fname", fName);

所以这段代码要做的是：

对您的数据库执行一条 SQL 语句，查看是否有与您提供的名字匹配的名字。如果是这种情况，该人将被存储在 Person 对象中（请参阅下面的类答案）。如果没有匹配，则 Person 对象的属性将为null.

显然我不完全知道你要做什么，所以有几点需要注意： 当有超过 1 个人的名字匹配时，只有最后一个会被保存并返回给你。如果您希望能够存储这些数据，可以将它们添加到List<Person>.

Person 类使其更清洁：

 public class Person
    {
            public string firstName { get; set; }
            public string lastName { get; set; }
    }

现在调用该方法：

Person x = SomeMethod("John");

然后，您可以使用来自 Person 对象的值填充文本框，如下所示：

txtLastName.Text = x.LastName;
于 2013-01-05T13:05:48.840 回答
4

创建一个名为 DbManager 的类：

Class DbManager
{
 SqlConnection connection;
 SqlCommand command;

       public DbManager()
      {
        connection = new SqlConnection();
        connection.ConnectionString = @"Data Source=.     \SQLEXPRESS;AttachDbFilename=|DataDirectory|DatabaseName.mdf;Integrated Security=True;User Instance=True";
        command = new SqlCommand();
        command.Connection = connection;
        command.CommandType = CommandType.Text;
     } // constructor

 public bool GetUsersData(ref string lastname, ref string firstname, ref string age)
     {
        bool returnvalue = false;
        try
        {
            command.CommandText = "select * from TableName where firstname=@firstname and lastname=@lastname";
            command.Parameters.Add("firstname",SqlDbType.VarChar).Value = firstname;
 command.Parameters.Add("lastname",SqlDbType.VarChar).Value = lastname; 
            connection.Open();
            SqlDataReader reader= command.ExecuteReader();
            if (reader.HasRows)
            {
                while (reader.Read())
                {

                    lastname = reader.GetString(1);
                    firstname = reader.GetString(2);

                    age = reader.GetString(3);


                }
            }
            returnvalue = true;
        }
        catch
        { }
        finally
        {
            connection.Close();
        }
        return returnvalue;

    }

然后双击表单上的检索按钮（例如 btnretrieve）并插入以下代码：

 private void btnretrieve_Click(object sender, EventArgs e)
    {
        try
        {
            string lastname = null;
            string firstname = null;
            string age = null;

            DbManager db = new DbManager();

            bool status = db.GetUsersData(ref surname, ref firstname, ref age);
                if (status)
                {
                txtlastname.Text = surname;
                txtfirstname.Text = firstname;
                txtAge.Text = age;       
               }
          }
       catch
          {

          }
   }
于 2014-03-17T13:16:57.587 回答
2

从数据库中检索数据：

private SqlConnection Conn;
 private void CreateConnection()
 {
    string ConnStr =
    ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
    Conn = new SqlConnection(ConnStr);
 }
 public DataTable getData()
 {
 CreateConnection();
    string SqlString = "SELECT * FROM TableName WHERE SomeID = @SomeID;";
    SqlDataAdapter sda = new SqlDataAdapter(SqlString, Conn);
    DataTable dt = new DataTable();
    try
    {
        Conn.Open();
        sda.Fill(dt);
    }
    catch (SqlException se)
    {
        DBErLog.DbServLog(se, se.ToString());
    }
    finally
    {
        Conn.Close();
    }
    return dt;
}
于 2015-07-30T20:32:07.630 回答
2

设置连接后，您可以使用这个简单的方法：

private void getAgentInfo(string key)//"key" is your search paramter inside database
    {
        con.Open();
        string sqlquery = "SELECT * FROM TableName WHERE firstname = @fName";

        SqlCommand command = new SqlCommand(sqlquery, con); 
        SqlDataReader sReader;

        command.Parameters.Clear();
        command.Parameters.AddWithValue("@fName", key);
        sReader = command.ExecuteReader();

        while (sReader.Read())
        {
            textBoxLastName.Text = sReader["Lastname"].ToString(); //SqlDataReader
            //["LastName"] the name of your column you want to retrieve from DB

            textBoxAge.Text = sReader["age"].ToString();
            //["age"] another column you want to retrieve
        }
        con.Close();
    }

现在您可以通过 textBoxFirstName 将密钥传递给此方法，例如：

getAgentInfo(textBoxFirstName.Text);
于 2017-12-03T11:43:54.830 回答
1

我们可以使用这种类型的代码段，我们通常也使用这种代码来测试和验证 DB 到 API 字段的数据

class Db
{
    private readonly static string ConnectionString =
            ConfigurationManager.ConnectionStrings
                        ["DbConnectionString"].ConnectionString;
    public static List<string> GetValuesFromDB(string LocationCode)
    {
        List<string> ValuesFromDB = new List<string>();
        string LocationqueryString = "select BELocationCode,CityLocation,CityLocationDescription,CountryCode,CountryDescription " +
            $"from [CustomerLocations] where LocationCode='{LocationCode}';";
        using (SqlConnection Locationconnection =
                                 new SqlConnection(ConnectionString))
        {
            SqlCommand command = new SqlCommand(LocationqueryString, Locationconnection);
            try
            {
                Locationconnection.Open();
                SqlDataReader Locationreader = command.ExecuteReader();
                while (Locationreader.Read())
                {
                    for (int i = 0; i <= Locationreader.FieldCount - 1; i++)
                    {
                        ValuesFromDB.Add(Locationreader[i].ToString());
                    }
                }
                Locationreader.Close();
                return ValuesFromDB;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                throw;
            }
        }

    }

}

希望这可能会有所帮助

注意：你们需要连接字符串（在我们的例子中是“DbConnectionString”）

于 2019-04-09T06:16:55.980 回答
0 
    DataTable formerSlidesData = new DataTable();
    DformerSlidesData = searchAndFilterService.SearchSlideById(ids[i]);
                if (formerSlidesData.Rows.Count > 0)
                {
                    DataRow rowa = formerSlidesData.Rows[0];

                    cabinet = Convert.ToInt32(rowa["cabinet"]);
                    box = Convert.ToInt32(rowa["box"]);
                    drawer = Convert.ToInt32(rowa["drawer"]);
                }
于 2020-05-19T13:54:29.680 回答