I am attempting to populate a DataGridViewComboBoxColumn with a list of strings then select one of them based upon their value on form load.
A simple task one would think, but I just can't get it right.
I am populating a DataGridViewComboBoxColumn with strings as such without a problem:
ComboBoxColumn.Items.AddRange("Mr.", "Ms.", "Mrs.", "Dr.");
I also seem to be able to add it to the DataGridView without a problem (This is incorrect see Edit):
ExampleDataGrid.Rows.Add("", ComboBoxColumn, 1000, "");
Now I want to set "Mr." to be selected on load. Other posts suggest that I should be able to simply use:
ExampleDataGrid.Rows[i].Cells["ExampleColumnName"].Value = "Mr.";
But whenever I use it, I get an error that tells me the value is not valid.
Is there something I'm missing?
I can however use this to get the set value without issue:
string Title = ExampleDataGrid.Rows[i].Cells["ExampleColumnName"].Value;
I had a look at the documentation but it doesn't seem to mention how to actually use .Value in this context.
Microsoft Docs
Any thoughts on where I am going wrong would be great.
Edit:
The issue I was having was caused by me setting the ComboBoxItems in the
"ExampleDataGrid.Rows.Add()". This should actually contain the value you want to set. e.g.
ExampleDataGrid.Rows.Add("", "Mr.", 1000, "");
You can initialize the DataGridView this way:
private void Form1_Load(object sender, EventArgs e)
{
var textBoxColumn = new DataGridViewTextBoxColumn();
textBoxColumn.Name = "textBoxColumn";
var comboBoxColumn = new DataGridViewComboBoxColumn();
comboBoxColumn.Items.AddRange("A", "B", "C");
comboBoxColumn.Name = "comboBoxColumn";
dataGridView1.Columns.Add(textBoxColumn);
dataGridView1.Columns.Add(comboBoxColumn);
dataGridView1.Rows.Add("1", "A");
dataGridView1.Rows.Add("2", "B");
}
And then update the value of the comboBoxColumn for the second row this way:
private void button1_Click(object sender, EventArgs e)
{
//You can use either of the following ways:
dataGridView1[1, 1].Value = "C";
//dataGridView1["comboBoxColumn", 1].Value = "C";
//dataGridView1.Rows[1].Cells["comboBoxColumn"].Value = "C";
//dataGridView1.Rows[1].Cells[1].Value = "C";
}
The value which you set for the cell, should be between the values which you added to Items of the DataGridViewComboBoxColumn.
Related
I follow this instructions to create multi select combobox
So I have something like this:
var empList = db.GetTableBySQL($"exec getTaskAssignableEmployeeList");
checkBoxComboBox1.DataSource = new Utility.ListSelectionWrapper<DataRow>(empList.Rows, "Abbreviation");
checkBoxComboBox1.DisplayMemberSingleItem = "Name";
checkBoxComboBox1.DisplayMember = "NameConcatenated";
checkBoxComboBox1.ValueMember = "Selected";
checkBoxComboBox1.Tag = empList.Rows;
checkBoxComboBox1.SelectedValueChanged += ComboEmployee_SelectedValueChanged;
As you can see I have ComboEmployee_SelectedValueChanged Event. So when I click into one checkbox I want to retrieve value of comboBox as:
private void ComboEmployee_SelectedValueChanged(object sender, EventArgs e)
{
var db = new SQLConnMgr();
var employeeComboBox = sender as CheckBoxComboBox;
var taskDataRow = employeeComboBox.Tag as DataRow;
var taskTypeName = taskDataRow["Name"] as string;
}
But I'm getting error because taskDataRow is always null, then when it try to execute var taskTypeName = taskDataRow["Name"] as string; I'm getting:
Object reference not set to an instance of an object.'
Why I cant retrieve taskDataRow fro\m comboBox? Regards
If you want to know which items are selected, you have two options:
Use the CheckBoxItems property on the ComboBox which is a list of items wrapping each item in the ComboBox.Items list. The CheckBoxComboBoxItem class is a standard CheckBox, and therefore the bool value you are looking for is contained in Checked.
Or if you stored a reference to the ListSelectionWrapper<T>, you could use that to access the Selected property of the binded list.
-
if (ComboBox.CheckBoxItems[5].Checked)
DoSomething();
OR
if (StatusSelections.FindObjectWithItem(UpdatedStatus).Selected)
DoSomething();
You are getting Null Reference exception because you have saved table.Rows in the tag of the combobox not the DataRow in the below line that why you are getting exception.
var taskDataRow = employeeComboBox.Tag as DataRow;
To resolve the issue, Iterate through CheckBoxItems and there you can
get the selected item text. After that filter the data rows on the
basis of selected item text or value.
private void c1TrueDBGrid1_Click(object sender, EventArgs e)
{
}
How can I get the value of a cell and then display it in a textbox.
Just like this code that works for data grid view "OwnerIDtxtbox.Text = PetGrid.Rows[i].Cells[7].Value.ToString();"
c1TrueDBGrid exposes a couple of indexers that takes the row number as first parameter and the column name or index as the second - you can use either one of them.
Please note that both returns object.
var row = grid.Row; // get the current row
var columnIndex = 0;
var cellValue = grid[row, "ColumnName"];
var cellValue = grid[row, columnIndex];
Another option is to use
var value = grid.Columns[0].CellValue(row);
And of course, you can use the column's string indexer:
var value = grid.Columns["Company"].CellValue(row)
For more information, please refer to official documentation.
Sorry if it has some obvious solution, but I am trying to solve it for hours but could not find a solution.
I use several ComboBoxes in my WindowsFormsApplication to relate ids with names. The problem is that when a user select an item from the combobox list, it works fine, but when he types an item, the SelectedValue property of the combobox is null.
To simulate the problem, I created a from with one button and a combobox.
In my actual application, I populate the comboboxes with data from tables in a sqlserver database, but for simplicity, here I populate it with a list:
public Form1()
{
InitializeComponent();
List<KeyValuePair<short,short>> l = new List<KeyValuePair<short,short>>();
l.Add(new KeyValuePair<short,short>(1,10));
l.Add(new KeyValuePair<short,short>(2,20));
l.Add(new KeyValuePair<short,short>(3,30));
this.comboBox1.DataSource = l;
this.comboBox1.DisplayMember = "Value";
this.comboBox1.ValueMember = "Key";
}
private void button1_Click(object sender, EventArgs e)
{
if (this.comboBox1.SelectedValue == null)
MessageBox.Show("NULL");
else
MessageBox.Show(this.comboBox1.SelectedValue.ToString());
}
For example, when user select the second item (20) from the list and clicks on the button, messagebox shows 2 as it is expected, but if he types the number 20 into the combobox, the SelectedValue is null.
This problem could be solved by changing the style of combobox:
this.comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
But it prevents user to type into the combobox, so I am forced to use the default ComboBoxStyle.DropDown.
Thats because the combo box does not select the item that you have typed. Add this option
comboBox1.AutoCompleteMode = AutoCompleteMode.Suggest;
Then it will select the item when ever it was able to find it.
By default it is set to AutoCompleteMode.None.
(I think) This is mainly designed for suggestions but it can solve your problem here. also if you want to show the suggestions:
comboBox1.AutoCompleteSource = AutoCompleteSource.ListItems;
by default it is set to AutoCompleteSource.None.
https://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.autocompletemode%28v=vs.110%29.aspx
An option that you have is using the EventHandler on the comboBox1.TextChange event that will allow you to personally handle how the text is translated into the different options.
This can be added to the designer (similar to a button).
this.comboBox1.TextChanged += new System.EventHandler(this.UpdateValue);
Then depending on how want to read the results and see if you have a match you can create a converter, use another key/value, or you can do a boring old tryparse as I will show you. You will need the list as a property that you can reference to see if you have found the proper results.
private void UpdateValue(object sender, EventArgs e)
{
short result;
if (short.TryParse(comboBox1.Text, out result))
{
var matches = from val in l where val.Value == result select val.Key;
{
foreach (short m in matches)
this.comboBox1.SelectedValue = m;
}
}
}
Good luck! Let me know if you need more examples with the event handler. Don't forget to vote.
Question about the ListBox.DataBinding method. I'm loading a listbox with a DataRows array object and I want to check for each DataRow element a column value if its true/false. If the column value is true, then modify the style for the current listBox.ListItem object. Below is some sample code.:
System.Data.DataRow[] rows = Data.SchoolDetails.Select(filter);
lstBox.DataBinding += new EventHandler(lstBox_DataBinding);
lstBox.DataSource = rows;
lstBox.DataTExtField = "Value";
lstBox.DataValueField = "ValueCode";
lstBox.DataBind();
static void lstBox_DataBinding(object sender, EventArgs e)
{
ListBox l = (ListBox) sender;
}
You can't really do that with a ListBox. Maybe you should use ListView, which supports an ItemDataBinding event for each item.
The best answer is probably the one you included in the comment above.
As an alternative I can just loop through the DataRow array and do it that way, and set the style by doing this: lstBox.Items.Add(new ListItem("").Attributes.CssStyle.Add(HtmlTextWriterStyle.FontWeight, "Bold"));. Thanks for hte help. – Brandon Michael Hunter
That is exactly how I'd do it.
I'm using a DataGridView binding its datasource to a List, and specifying the properties for each column.
An example would be:
DataGridViewTextBoxColumn colConcept = new DataGridViewTextBoxColumn();
DataGridViewCell cell4 = new DataGridViewTextBoxCell();
colConcept.CellTemplate = cell4;
colConcept.Name = "concept";
colConcept.HeaderText = "Concept";
colConcept.DataPropertyName = "Concept";
colConcept.Width = 200;
this.dataGridViewBills.Columns.Add(colConcept);
{... assign other colums...}
And finally
this.dataGridViewBills.DataSource=billslist; //billslist is List<Bill>
Obviously Class Bill has a Property called Concept, as well as one Property for each column.
Well, now my problem, is that Bill should have and Array/List/whateverdynamicsizecontainer of strings called Years.
Let's assume that every Bill will have the same Years.Count, but this only known at runtime.Thus, I can't specify properties like Bill.FirstYear to obtain Bill.Years[0], Bill.SecondYear to obtain Bills.Years[1]... etc... and bind it to each column.
The idea, is that now I want to have a grid with dynamic number of colums (known at runtime), and each column filled with a string from the Bill.Years List. I can make a loop to add columns to the grid at runtime depending of Bill.Years.Count, but is possible to bind them to each of the strings that the Bill.Years List contains???
I'm not sure if I'm clear enough.
The result ideally would be something like this, for 2 bills on the list, and 3 years for each bill:
--------------------------------------GRID HEADER-------------------------------
NAME CONCEPT YEAR1 YEAR2 YEAR3
--------------------------------------GRID VALUES-------------------------------
Bill1 Bill1.Concept Bill1.Years[0] Bill1.Years[1] Bill1.Years[2]
Bill2 Bill2.Concept Bill2.Years[0] Bill2.Years[1] Bill2.Years[2]
I can always forget the datasource, and write each cell manually, as the MSFlexGrid used to like, but if possible, I would like to use the binding capabilities of the DataGridView.
Any ideas? Thanks a lot.
I recently ran into this same problem. I ended up using DataGridView's virtual mode instead of binding to a data source. It doesn't have exactly the same features as binding, but it's still a lot more powerful than populating each cell manually.
In virtual mode, the DataGridView will fire an event whenever it needs to display a cell, which essentially means you can populate the cell however you please:
private void my_init_function() {
datagridview.VirtualMode = true;
datagridview.CellValueNeeded += new System.Windows.Forms.DataGridViewCellValueEventHandler(datagridview_CellValueNeeded);
}
private void datagridview_CellValueNeeded(object sender, DataGridViewCellValueEventArgs e)
{
e.Value = get_my_data(e.RowIndex, e.ColumnIndex);
}
You could use reflection to set up and fill the DataGridView. I've done this with a single type, but I don't see why it couldn't be extended to your data structure.
To set up the DataGridView:
// Create the columns based on the data in the album info - get by reflection
var ai = new AlbumInfo();
Type t = ai.GetType();
dataTable.TableName = t.Name;
foreach (PropertyInfo p in t.GetProperties())
{
// IF TYPE IS AN ARRAY (OR LIST) THEN ADD A COLUMN FOR EACH ELEMENT
var columnSpec = new DataColumn();
// If nullable get the underlying type
Type propertyType = p.PropertyType;
if (IsNullableType(propertyType))
{
var nc = new NullableConverter(propertyType);
propertyType = nc.UnderlyingType;
}
columnSpec.DataType = propertyType;
columnSpec.ColumnName = p.Name;
dataTable.Columns.Add(columnSpec);
}
dataGridView.DataSource = dataTable;
Then to populate the DataGridView:
// Add album info to table - add by reflection
var ai = new AlbumInfo();
Type t = ai.GetType();
// WOULD NEED TO INCREASE BY LENGTH OF ARRAY
var row = new object[t.GetProperties().Length];
int index = 0;
foreach (PropertyInfo p in t.GetProperties())
{
// IF TYPE IS AN ARRAY (OR LIST) THEN ADD EACH ELEMENT
row[index++] = p.GetValue(info, null);
}
dataTable.Rows.Add(row);
This is just the code I used, so you'll have to modify the code to handle your year array/list.