使用ComboBox在DataGridView中显示二级属性

Question

As I understand it, ComboBox columns are more dynamic for binding in DataGridView than standard columns, and this flexibility can be used to use DisplayMembers from second-order properties. This approach is the first mentioned here by Mr. Aghaei .

However, I'm not getting it right. My application still throws the exception that "Name" doesn't exist.

 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;                                                                               
        }

Here is the class definition:

     
    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})";
            }

        }
    }

And the definition for TitleModel:

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

    }
}

Answer 1

To support the post Show Properties of a Navigation Property in DataGridView (Second Level Properties) I've already shared a few example in the same post or this one which allows showing second level properties and allow editing them.

Here I will share a few more examples, each example has been written as a minimal complete verifiable example, you can just copy and paste in an empty form and they will work.

These are the examples:

• Using ToString()
• Using CellFormatting
• Using ComboBox Column for Navigation Object
• Using ComboBox Column for Foreign key column

Example - Using ToString()

When: You don't want to change JobTitle of Employee

How: By overriding ToString method of JobTitle

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);
}

Example - Using CellFormatting

When: You don't want to change JobTitle of Employee

How: By handling CellFormatting event of DataGridView and setting Value of the event args to a string representation of JobTitle

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);
}

Example - Using ComboBox Column for Foreign key column

When: You want to be able to change the JobTitle of Employee and you have the foreign key column in your model.

How: Using a DataGridViewComboBoxColumn for that property, having a data source containing all job titles, and setting DisplayMember and ValueMember to proper properties.

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);
}

Example - Using ComboBox Column for Navigation Object

When: You want to be able to change the JobTitle of Employee and you don't have the foreign key column in your model, instead you want to use the navigation object in your model.

How: Using a DataGridViewComboBoxColumn for that property, having a data source containing all job titles, without setting DisplayMember and ValueMember to proper properties. Then handling CellFormatting to set the display value of the cell and handling CellParsing to get value from ComboBox and put into the cell.

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);
}