如何将combobox1项目从form1传递到form2中的combobox2答案

【问题标题】：How to pass combobox1 items from form1 to combobox2 in form2如何将combobox1项目从form1传递到form2中的combobox2
【发布时间】：2021-01-14 02:18:37
【问题描述】：

我有两个组合框（表单 1 中的组合框 1 和表单 2 中的组合框 2）。我需要导入一个 excel 文件，并且 combobox1 获取工作表名称。然后在form2中（我不想再次导入同一个文件）我有combobox2，它也具有与combobox1相同的工作表名称。

我试过这个，但我得到了 NULLFUNCTION 表达式的错误（附加信息：对象引用未设置为对象的实例）。

 using (OpenFileDialog openFileDialog = new OpenFileDialog() { Filter = "Excel 97-2003 Workbook|*.xls|Excel Workbook|*.xlsx |fichiers Textes (*.txt)|*.txt|fichiers CSV (*.csv)|*.csv|tous les fichiers (*.*)|*.*" })
            {
                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                    TextBox_Emplacement.Text = openFileDialog.FileName;
                    using (var stream = File.Open(openFileDialog.FileName, FileMode.Open, FileAccess.Read))
                    {
                        using (IExcelDataReader reader = ExcelReaderFactory.CreateReader(stream))
                        {
                            DataSet result = reader.AsDataSet(new ExcelDataSetConfiguration()
                            {
                                ConfigureDataTable = (_) => new ExcelDataTableConfiguration() { UseHeaderRow = true }
                            });
                            dataTableCollection = result.Tables; 
                            dataTableCollection1 = result.Tables;
                            sheet.Items.Clear();
                            //cp.radDropDownList1.Items.Clear();
                            foreach (DataTable table in dataTableCollection)
                                sheet.Items.Add(table.TableName);//add sheet to combobox

                           **Form_Copie cp1 = (Form_Copie)Application.OpenForms["Form_Copie"];
                           foreach (DataTable table in dataTableCollection)
                              cp1.radDropDownList1.Items.Add(table.TableName);//add sheet to combobox**

【问题讨论】：

Interaction between forms — How to change a control of a form from another form?

标签： c# excel winforms

【解决方案1】：

如果您尝试传递的项目只是组合框字符串值可以在加载新表单时传递值

{
string sheet = comboBox1.Text;
Form frm2 = new Form2(sheet);
frm2.show();
}

Public Form2(string sheet)
{
Initialize();
comboBox2.Text = sheet;
}

【讨论】：

【解决方案2】：

有几种方法可以做到这一点。重载构造函数是一种好方法，但对每个控件执行此操作很快就会变得令人生畏和混乱。如果您想对多个控件执行此操作，我建议使用包含绑定属性（例如 System.ComponentModel.BindingList 和/或 System.Forms.Binding）作为每个表单中的字段的模型。然后重载构造函数，通过模型类传入绑定。

public class BindingModel {
    public property BindingList<string> ComboBoxBinding {get;set;}
    ... other binding/non-binding properties ...
}

public class Form1{
    private BindingModel _bindingModel = new _bindingModel();

    private void Form1_Shown(object sender, EventArgs e) {
        this.ComboBox1.DataSource = _bindingModel.ComboBoxBinding;
        this.ComboBox1.DataMember = "";

        // the add would go in your excel method
        _bindingModel.ComboBoxBinding.Add("Item 1");
    }

    private void btnOpenForm2_Click(object sender, EventArgs e) {
        var frm = new Form2(_bindingModel);
        frm.Show();
        this.Close();
    }
}

public class Form2{
    private BindingModel _bindingModel = new _bindingModel();
    
    public void Form2(BindingModel bindingModel){
        this._bindingModel = bindingModel;
    }

    // Once the form is shown bind the ComboBox and it will populate the values
    private void Form2_Shown(object sender, EventArgs e){
        this.ComboBox1.DataSource = _bindingModel.ComboBoxBinding;
        this.ComboBox1.DataMember = "";
    }
}

或者，可以在调用表单中设置控件项：

public class Form1{
    private void btnOpenForm2_Click(object sender, EventArgs e) {
        var frm = new Form2();
        for(int i = 0; i < this.ComboBox1.Count - 1; i++){
            frm.ComboBox1.Items.Add(ComboBox1.Items[i]);
        }
        frm.Show();
        this.Close();
    }
}

【讨论】：