使用 ComboBox 在 DataGridView 中显示二级属性

Question

据我了解，ComboBox 列在 DataGridView 中的绑定比标准列更具动态性，并且这种灵活性可用于从二阶属性中使用 DisplayMembers。这种方法是hereMr. Aghaei第一次提到的。

但是，我没有做对。我的应用程序仍然抛出“名称”不存在的异常。

 public void CreateEmployeeTable()
        {

            DataGridViewComboBoxColumn jobTitleColumn = new DataGridViewComboBoxColumn();
            jobTitleColumn.HeaderText = "Job Title";
            jobTitleColumn.DataPropertyName = "JobTitle";
            jobTitleColumn.DisplayStyle = DataGridViewComboBoxDisplayStyle.Nothing;
            jobTitleColumn.DataPropertyName = "ID";
            jobTitleColumn.DataSource = globalEmployeeList;
            jobTitleColumn.ValueMember = "ID";
            jobTitleColumn.DisplayMember = "Name";
            jobTitleColumn.ReadOnly = true;

            employeeGridView.AutoGenerateColumns = false;
            employeeGridView.ColumnCount = 2;
            employeeGridView.Columns[0].HeaderText = "Employee ID";
            employeeGridView.Columns[0].DisplayIndex = 0;
            employeeGridView.Columns[0].DataPropertyName = "ID";
            employeeGridView.Columns[1].HeaderText = "Name";
            employeeGridView.Columns[1].DataPropertyName = "ListView";
            employeeGridView.Columns[1].AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
            employeeGridView.Columns.Add(jobTitleColumn);
            
            employeeGridView.DataSource = globalEmployeeList;                                                                               
        }

这是类定义：

     
    public class EmployeeModel
    {
        public int ID { get; set; }
        public string LastName { get; set; }
        public string FirstName { get; set; }
        public string Nickname { get; set; }
        public DepartmentModel Department { get; set; }
        public TitleModel JobTitle { get; set; }
        public DateTime HireDate { get; set; }
        public List<EmailModel> EmailList { get; set; } = new List<EmailModel>();
        public List<PhoneModel> PhoneList { get; set; } = new List<PhoneModel>();
        public List<RestrictionModel> RestrictionsList { get; set; } = new List<RestrictionModel>();
        public List<CitationModel> CitationsList { get; set; } = new List<CitationModel>();
        public List<CertificationModel> CertificationList { get; set; } = new List<CertificationModel>();

        public string ListView
        {
            get
            {
                return $"{LastName}, {FirstName}";
            }
        }

        public string ToEmailString()
        {
            IEnumerable<string> employeeEmailStrings = EmailList.Select(emmod => emmod.ToString());
            string employeeEmailString = string.Join($"{Environment.NewLine}", employeeEmailStrings);

            IEnumerable<string> certificationStrings = CertificationList.Select(clistmod => clistmod.ToString());
            string certificationString = string.Join($"{Environment.NewLine}", certificationStrings);

            IEnumerable<string> phoneStrings = PhoneList.Select(plistmod => plistmod.ToString());
            string phoneString = string.Join($"{Environment.NewLine}", phoneStrings);

            return $"{FirstName}, {LastName}: {Environment.NewLine} -{JobTitle.Name}- {Environment.NewLine} {employeeEmailString} {Environment.NewLine} {certificationString} {Environment.NewLine} {phoneString}";
        }



        public class EmailModel
        {
            public int ID { get; set; }
            public string Address { get; set; }
            public string Type { get; set; }

            public override string ToString()
            {
                return $"{Address} ({Type})";
            }
        }

        public class PhoneModel
        {
            public int ID { get; set; }
            public string Number { get; set; }
            public string Type { get; set; }
            public override string ToString()
            {
                return $"{Number} ({Type})";
            }

        }
    }

以及 TitleModel 的定义：

    public class TitleModel
    {
        public string Name { get; set; }
        public int ID { get; set; }  

    }
}

Answer 1

为了支持帖子Show Properties of a Navigation Property in DataGridView (Second Level Properties)，我已经在同一个帖子或this one 中分享了一些示例，它允许显示二级属性并允许对其进行编辑。

这里我再分享几个例子，每个例子都写成一个最小的完整的可验证的例子，你可以复制粘贴到一个空的表格中，它们就可以工作了。

这些是例子：

• 使用 ToString()
• 使用单元格格式
• 为导航对象使用组合框列
• 为外键列使用组合框列

示例 - 使用 ToString()

何时：您不想更改员工的JobTitle

如何：通过覆盖JobTitle的ToString方法

class JobTitle
{
    public int Id { get; set; }
    public string Name { get; set; }
    public override string ToString()
    {
        return Name;
    }
}
class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public JobTitle JobTitle { get; set; }
}
protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    var jobTitles = new List<JobTitle>() {
        new JobTitle {Id= 1, Name="Manager" },
        new JobTitle {Id= 2, Name="Employee" },
    };
    var employees = new List<Employee>() {
        new Employee{ Id = 1, Name ="John", JobTitle = jobTitles[0] },
        new Employee{ Id = 2, Name ="Jane", JobTitle = jobTitles[1] },
        new Employee{ Id = 3, Name ="Jack", JobTitle = jobTitles[1] },
    };
    var dg = new DataGridView();
    dg.Dock = DockStyle.Fill;
    dg.DataSource = employees;
    this.Controls.Add(dg);
}

示例 - 使用单元格格式化

何时：您不想更改员工的JobTitle

如何：通过处理DataGridView的CellFormatting事件并将事件参数的Value设置为JobTitle的字符串表示形式

class JobTitle
{
    public int Id { get; set; }
    public string Name { get; set; }
}
class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public JobTitle JobTitle { get; set; }
}
protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    var jobTitles = new List<JobTitle>() {
        new JobTitle {Id= 1, Name="Manager" },
        new JobTitle {Id= 2, Name="Employee" },
    };
    var employees = new List<Employee>() {
        new Employee{ Id = 1, Name ="John", JobTitle = jobTitles[0] },
        new Employee{ Id = 2, Name ="Jane", JobTitle = jobTitles[1] },
        new Employee{ Id = 3, Name ="Jack", JobTitle = jobTitles[1] },
    };
    var dg = new DataGridView();
    dg.Dock = DockStyle.Fill;
    dg.DataSource = employees;
    dg.CellFormatting += (obj, args) =>
    {
        if (args.RowIndex >= 0 &&
            dg.Columns[args.ColumnIndex].DataPropertyName == "JobTitle")
            args.Value = ((Employee)dg.Rows[args.RowIndex].DataBoundItem).JobTitle.Name;
    };
    this.Controls.Add(dg);
}

示例 - 将 ComboBox 列用于外键列

何时：您希望能够更改 Employee 的 JobTitle，并且您的模型中有外键列。

如何：为该属性使用DataGridViewComboBoxColumn，拥有一个包含所有职位的数据源，并将DisplayMember 和ValueMember 设置为适当的属性。

class JobTitle
{
    public int Id { get; set; }
    public string Name { get; set; }
}
class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int JobTitleId { get; set; }
}
protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    var jobTitles = new List<JobTitle>() {
        new JobTitle {Id= 1, Name="Manager" },
        new JobTitle {Id= 2, Name="Employee" },
    };
    var employees = new List<Employee>() {
        new Employee{ Id = 1, Name ="John", JobTitleId = 1 },
        new Employee{ Id = 2, Name ="Jane", JobTitleId = 2 },
        new Employee{ Id = 2, Name ="Jack", JobTitleId = 2 },
    };
    var dg = new DataGridView();
    dg.Dock = DockStyle.Fill;
    dg.DataSource = employees;
    dg.Columns.Add(new DataGridViewTextBoxColumn() 
    { 
        DataPropertyName = "Id", HeaderText = "Id" 
    });
    dg.Columns.Add(new DataGridViewTextBoxColumn() 
    {
        DataPropertyName = "Name", HeaderText = "Name" 
    });
    dg.Columns.Add(new DataGridViewComboBoxColumn()
    {
        DataPropertyName = "JobTitleId",
        HeaderText = "JobTitleId",
        DataSource = jobTitles,
        ValueMember = "Id",
        DisplayMember = "Name",
    });
    this.Controls.Add(dg);
}

示例 - 将 ComboBox 列用于导航对象

何时：您希望能够更改 Employee 的 JobTitle 并且您的模型中没有外键列，而是希望使用导航对象你的模型。

如何： 为该属性使用 DataGridViewComboBoxColumn，具有包含所有职位的数据源，而不将 DisplayMember 和 ValueMember 设置为适当的属性。然后处理CellFormatting设置单元格的显示值，处理CellParsing从ComboBox获取值并放入单元格中。

class JobTitle
{
    public int Id { get; set; }
    public string Name { get; set; }
    public override string ToString()
    {
        return Name;
    }
}
class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public JobTitle JobTitle { get; set; }
}

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    var jobTitles = new List<JobTitle>() {
        new JobTitle {Id= 1, Name="Manager" },
        new JobTitle {Id= 1, Name="Employee" },
    };
    var employees = new List<Employee>() {
        new Employee{ Id = 1, Name ="John", JobTitle = jobTitles[0] },
        new Employee{ Id = 2, Name ="Jane", JobTitle = jobTitles[1] },
        new Employee{ Id = 2, Name ="Jack", JobTitle = jobTitles[1] },
    };
    var dg = new DataGridView();
    dg.Dock = DockStyle.Fill;
    dg.DataSource = employees;
    dg.Columns.Add(new DataGridViewTextBoxColumn() 
    { 
        DataPropertyName = "Id", HeaderText = "Id" 
    });
    dg.Columns.Add(new DataGridViewTextBoxColumn() 
    {
        DataPropertyName = "Name", HeaderText = "Name" 
    });
    dg.Columns.Add(new DataGridViewComboBoxColumn()
    {
        DataPropertyName = "JobTitle",
        HeaderText = "JobTitle",
        DataSource = jobTitles,
    });
    dg.CellFormatting += (obj, args) =>
    {
        if (args.RowIndex >= 0 &&
            dg.Columns[args.ColumnIndex].DataPropertyName == "JobTitle")
        {
            args.Value = 
        ((Employee)dg.Rows[args.RowIndex].DataBoundItem).JobTitle.ToString();
        }
    };
    dg.CellParsing += (obj, args) =>
    {
        if (args.RowIndex >= 0 &&
            dg.Columns[args.ColumnIndex].DataPropertyName == "JobTitle")
        {
            args.Value = ((ComboBox)dg.EditingControl).SelectedItem;
            args.ParsingApplied = true;
        }
    };
    this.Controls.Add(dg);
}