Question

我试图在组合框中设置值，但每次我尝试这样我都会得到结果＆＃39; null＆＃39;。我是否定义了错误的价值，或者我是否试图以错误的方式获得价值？

// Setting the value
sqlCmd.CommandText = "SELECT Id, Ime FROM Unajmljivaci WHERE Aktivan = 0";
conn.Open();
using (var reader = sqlCmd.ExecuteReader())
{
    while (reader.Read())
    {
         cmbUnajmljivaci.Items.Add(new { Id = reader["Id"].ToString(), Ime = reader["Ime"].ToString() });
    }
    cmbUnajmljivaci.ValueMember = "Id";  // <---
    cmbUnajmljivaci.DisplayMember = "Ime";
}

//Retrieving the value
sqlCmd.Parameters.AddWithValue("@SifraUnajmljivca", Convert.ToString(cmbUnajmljivaci.SelectedValue));

Answer 1

您需要设置组合框的数据源。

Answer 2

            using (SqlConnection sqlConn = new SqlConnection("CONNECTION STRING"))
            {
              DataSet ds = new DataSet();
              SqlCommand sqlCmd = sqlConn.CreateCommand();
              sqlConn.Open();
              SqlDataAdapter SQA_DataAdapter = new SqlDataAdapter(sqlCmd);
              SQA_DataAdapter.SelectCommand = new SqlCommand("SELECT Id, Ime FROM Unajmljivaci WHERE Aktivan = 0", sqlConn);
              SQA_DataAdapter.Fill(ds, "Table");
              if (ds != null)
                if (ds .Tables.Count > 0)
                {
                  cmbUnajmljivaci.ValueMember = "Id";
                  cmbUnajmljivaci.DisplayMember = "Ime";
                  cmbUnajmljivaci.DataSource = ds.Tables[0];
                }
              sqlConn.Close();
            }

Answer 3

尝试获取这样的值：

dynamic dyn = cmbUnajmljivaci.SelectedItem;
string s = dyn.Id;

甚至可以像这样内联：

//Retrieving the value
sqlCmd.Parameters.AddWithValue("@SifraUnajmljivca", Convert.ToString(((dynamic)cmbUnajmljivaci.SelectedItem).Id);

Answer 4

参考问题的示例代码，

    DataSet ds = new DataSet();
    DataTable dt = ds.Tables.Add();
    dt.Columns.Add("ID");
    dt.Columns.Add("Name");
    dt.Rows.Add("0", "Item1");
    dt.Rows.Add("1", "Item2");

要插入具有指定索引的项目，您需要使用以下代码

 //Insert the item into the collection with specified index
        foreach (DataRow row in dt.Rows)
        {
            int id = Convert.ToInt32(row["ID"]);
            string name=row["Name"].ToString();
            comboBox1.Items.Insert(id,name);

        }

始终索引应该从 0（零）开始。

简单方法为组合框添加值

comboBox1.DataSource=dt;
comboBox1.DisplayMember = "Name";
comboBox1.ValueMember = "ID";

将值设置为ComboBoxs项目#C

4 个答案: