从数据库动态填充组合框

Question

我正在为我的大学开发一个项目，我需要将数据库中的数据绑定到组合框中。我需要将卷号/注册号存储在组合框的“值”字段中，并将学生姓名存储在组合框的“文本”属性中。

我的代码是：

#region 填充组合框 //填充组合框。 公共静态无效FillCombo（ComboBox _cb，字符串_sSQL，字符串_sTable） { OleDbDataAdapter _oledbDA = 新 OleDbDataAdapter(_sSQL, _olbedbCN); DataTable _dtSource = new DataTable(); _oledbDA.Fill(_dtSource); _cb.DataSource = _dtSource; _cb.ValueMember = _dtSource.Columns[0].ColumnName; _cb.DisplayMember = _dtSource.Columns[1].ColumnName; }

endregion

这里::

_sSQL = "select rollno, Studentname from Student_data"

我尝试过的其他代码是：

region Fill Combo Box

    //Fill Combo Box.
    public static void FillCombo(ComboBox _cb, string _sSQL, string _sTable)
    {


        OleDbDataAdapter _oledbDA = new OleDbDataAdapter("select rollno, studentname from student_data", _olbedbCN);
        DataTable _dtSource = new DataTable();
        _oledbDA.Fill(_dtSource);
        _cb.DataSource=ds.Tables["StudentData"];
        _cb.DisplayMember="Studentname";
        _cb.ValueMember="rollno";
        _cb.SelectedIndex=0;        }

}

endregion

但问题是，组合框中没有加载任何内容...当我运行该应用程序时，没有出现错误，但组合框中没有加载任何内容...

请帮助...它的 SOS...

Answer 1

我更喜欢使用从数据库检索的数据手动填充组合框。为此，我编写了一个类 MaskedValue，我每次都会使用它。
这是类（从 VB.NET 转换而来）

using System;
using System.Diagnostics;
using System.ComponentModel;

/// <summary>Represents a value masking an underlying value.</summary>
[DebuggerDisplay("{ToString()}"), DebuggerStepThrough()]
public class MaskedValue : IComparable<MaskedValue>, IComparer<MaskedValue>
{

    private string _value;
    public string Value {
        get { return _value; }
        set { _value = value; }
    }
    private object _underlyingValue;
    public object UnderlyingValue {
        get { return _underlyingValue; }
        set { _underlyingValue = value; }
    }

    /// <summary>Creates a new instance of the MaskedValue class.</summary>
    public MaskedValue()
    {
        Value = "";
        UnderlyingValue = null;
    }

    /// <summary>Creates a new instance of the MaskedValue class.</summary>
    /// <param name="value">Value to be assigned to the MaskedValue.</param>
    public MaskedValue(string value)
    {
        this.Value = value;
    }

    /// <summary>Creates a new instance of the MaskedValue class.</summary>
    /// <param name="value">Value to be assigned to the MaskedValue.</param>
    /// <param name="underlyingValue">Underlying value of the MaskedValue.</param>
    public MaskedValue(string value, object underlyingValue)
    {
        this.Value = value;
        this.UnderlyingValue = underlyingValue;
    }

    /// <summary>Gets a value that represents this MaskedValue.</summary>
    public override string ToString()
    {
        return Value;
    }

    /// <summary>Compares two instances of MaskedValue.</summary>
    /// <param name="x" >First MaskedValue to be compared.</param>
    /// <param name="y">Second MaskedValue to be compared.</param>
    /// <returns>
    /// A 32-bit signed integer indicating the lexical relationship between the two comparands.
    /// </returns>
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    public int Compare(MaskedValue x, MaskedValue y)
    {
        return x.CompareTo(y);
    }

    /// <summary>Compares this MaskedValue to the other.</summary>
    /// <param name="other">MaskedValue to compare this MaskedValue with.</param>
    /// <returns>
    /// A 32-bit signed integer indicating the lexical relationship between the two comparands.
    /// </returns>
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    public int CompareTo(MaskedValue other)
    {
        return this.Value.CompareTo(other.Value);
    }
}

要填充组合框，我编写如下代码

foreach (DataRow dr in _DataTable.Rows)
{
    _ComboBox.Items.Add(New MaskedValue(dr("Name").ToString(), dr("ID")));
}