I know that this was asked million times but I do not how to define my search,so please have patience.
I want to make method which is going to set some proprieties on control dynamical refer to sting sent to method.
something like this
public void SetGridColumnProperty(ref DataGridView grid,string columnName, string propretyName, string propertyValue )
{
grid.Columns[columnName].("I know this can't be done as this") = propertyValue;
}
I apologize if my question is hard to understand,
Here what I want to do
I am making WinForms app whic is using lot od Data Grid Views for displaying and editing data.
As I have needs to often change looks of my girds, add columns edit order and other My idea was to hold some kind of metadata for each DataGird on form, And when I showing form to user I want before I load
my form set properties of grid by join metadata and properties of specific grid.
I want to have config files separated of real code in XML or in DataBase so when I do edits on my application I do not have to recompile new code, Just change my xml and at next loding forom it looks as I like
First of all, There is no need to use ref keyword, because DataGridView is a reference type. Second, here is the solution:
public void SetGridColumnProperty(DataGridView grid, string columnName, string propertyName, object propertyValue)
{
DataGridViewColumn dgvColumn = grid.Columns[columnName];
typeof(DataGridViewColumn).GetProperty(propertyName).SetValue(dgvColumn, propertyValue, null);
}
Sample:
SetGridColumnProperty(dataGridView1, "ColumnName", "Width", 500);
Update: Check the CanWrite property of the PropertyInfo class before invoking the SetValue method.
OK so you're talking about Reflection. You can look up a lot of resources which will refer to the Reflection Namespace.
To get you started setting a property you'll proabably want to you use MethodInfo along the following lines:
MethodInfo invokedMethod = grid.GetType().GetProperty("propertyName").GetSetMethod();
invokedMethod.Invoke(targetObject, parameters);
you can use PropertyInfo to get the Property of an Control and assign its value
public void SetGridColumnProperty(ref DataGridView grid,string columnName, string propretyName, string propertyValue )
{
PropertyInfo pInfo = grid.GetType().GetProperty(propretyName);
if (pInfo != null)
{
TypeConverter tc = TypeDescriptor.GetConverter(pInfo.PropertyType);
if (tc.CanConvertFrom(Type.GetType(propertyValue.GetType().ToString())))
{
valToSet = tc.ConvertFromString(propertyValue);
pInfo.SetValue(grid, valToSet, null);
}
}
}
hope this helps
This can be done using reflection, look at GetProperties on the type you need this for. This will return an array of PropertyInfo objects for each property. Check if CanWrite returns true for the property you need and then use SetValue to set your property value.
Related
I have a class with an IList readonly property. I have created a simple extension method, AddCSV, to add multiple items to that list. I want to create an action delegate to populate the list via the extension method. So far, I have
private Action<TListPropertyContainer, TDataValue> CreateListPropertySetter<TListPropertyContainer, TDataValue>(string listName)
{
var list = typeof(TListPropertyContainer).GetProperty(listName);
var method = typeof(Extensions).GetMethod("AddCSV");
return (Action<TListPropertyContainer, TDataValue>)Delegate.CreateDelegate(typeof(Action<TListPropertyContainer, TDataValue>), list, method);
}
but obviously this isn't working!
I am aware that there are other options. For example
a) I could inherit the list into my own customer class and add the AddCSV there
b) I could make items property read/write and set a fully populated list into my class
I'd be grateful if someone could correct me.
Many thx
Simon
There are two main problems.
You are trying to invoke the method on a PropertyInfo, not a list. To get the value of the property you would need to make a call to GetValue()
The call to GetMethod() doesn't specify binding flags. I suspect it might work better with GetMethod("AddCSV", BindingFlags.Public | BindingFlags.Static).
That being said, why are you instantiating it reflectively when you know the type and the method beforehand? It seems like you could just do:
private Action<TListPropertyContainer, TDataValue> CreateListPropertySetter<TListPropertyContainer, TDataValue>(string listName)
{
var propertyInfo = typeof(TListPropertyContainer).GetProperty(listName);
return (container,value) => {
var list = (IList<TDataValue>)propertyInfo.GetValue(container,null);
list.AddCSV(list);
};
}
If I am making incorrect assumptions about the signature of the extension method or the type of property, you can still do it with Delegate.CreateDelegate(), but take the comments about the PropertyInfo and the BindingFlags into account
You're trying to use list as the target of the delegate - but list is of type PropertyInfo, which sounds like it's not what you were expecting. Assuming you want to get the value of the property, and then call the method on that, you'll need to pass in the object containing the property as well, so you can get the actual list. (Alternatively, maybe it's "this" - you haven't really made that clear.) Either way, you can get the list itself and use that as the target. For example:
private Action<TListPropertyContainer, TDataValue>
CreateListPropertySetter<TListPropertyContainer, TDataValue>
(string listName, object target)
{
var listProperty = typeof(TListPropertyContainer).GetProperty(listName);
object list = listProperty.GetValue(target, null);
var method = typeof(Extensions).GetMethod("AddCSV");
return (Action<TListPropertyContainer, TDataValue>)Delegate.CreateDelegate(
typeof(Action<TListPropertyContainer, TDataValue>), list, method);
}
If this doesn't help, please edit your question with a short but complete console app demonstrating the problem. Right now there are too many unknowns to definitely help you.
Not sure if this is possible, but here is what I am trying to do:
I want to have a dictionary that contains a mapping of a column index to a property name used to populate that index.
In my code I will loop through an array if strings and use the dictionary to look up which column it should map to.
My end result code would look like:
for(int index = 0; index < fields.Length)
{
fieldPropertyMapping[index] = StripQuotes(fields[index]);
}
To do what you're asking specifically, you'll have to use reflection (as you tagged your question) to do this. Have a look at the PropertyInfo class. I'm not entirely certain what your code is doing, but a general example of reflectively setting a property value would be:
object targetInstance = ...; // your target instance
PropertyInfo prop = targetInstance.GetType().GetProperty(propertyName);
prop.SetValue(targetInstance, null, newValue);
You could, however, pass an Action<T> instead, if you know the property at some point in the code. For example:
YourType targetInstance = ...;
Action<PropertyType> prop = value => targetInstance.PropertyName = value;
... // in your consuming code
prop(newValue);
Or, if you know the type when you call it but you don't have the instance, you could make it an Action<YourType, PropertyType>. This also would prevent creating a closure.
Action<YourType, PropertyType> prop = (instance, value) => instance.PropertyName = value;
... // in your consuming code
prop(instance, newValue);
To make this fully generic ("generic" as in "non-specific", not as in generics), you'll probably have to make it an Action<object> and cast it to the proper property type within the lambda, but this should work either way.
You have a couple of choices:
Use reflection. Store and pass a PropertyInfo object into the method and set it's value through reflection.
Create an ActionDelegate with a closure to that property and pass that into the method.
you can use reflection to get the properties for a class:
var properties = obj.GetType().GetProperties();
foreach (var property in properties)
{
//read / write the property, here... do whatever you need
}
I need to loop through the properties of a custom object type that I'm getting back from the database and only show the columns that contain data.
This means I cannot simply bind the list of objects to the datagrid.
I don't want to loop through each object and see if the column is empty/null and determine in the UI to display it.
What I'm thinking is in my business layer before I send the object back I would send an IEnumerable back with only those columns that should be visible. Thus I was thinking of using Linq to Object to do this, but I'm not sure that would be very pretty.
Does anyone know of a solution that I could use without a ton of IF statements that I could do to check through a large object (30 or so columns) to determine what should be shown or not.
Foreach (CustomerData customerdata in Customers)
{
if (!customerdata.address.Equals(""))
{
dgvCustomerData.Column["Address"].visible = false;
}
//Continue checking other data columns...
}
I wish to avoid all of this in the UI and all the IFs...
I'm having a brain fart on this one can anyone help me?
Thanks
You could do the following to simplify it a bit
Action<T,string> del = (value,name) => {
if ( value.Equals("") ) {
dgvCustomerData.Column[name].Visible = false;
}
};
foreach ( var data in Customers ) {
del(data.address,"Address");
del(data.name, "Name");
...
}
Take a look at the .NET Reflection Libraries. You can use reflection to get ahold of all of an object's properties, and loop through them to find out if they are null or not. Then you could return a collection of KeyValuePair objects where Key = property name, and Value = true/false. You'd then use the keyvaluepairs to set column visibility...
I'm trying to write a custom method to populate a ListView control using Generics:
private void BindDataToListView(List<T> containerItems)
{
this.View = View.Details;
this.GridLines = true;
this.FullRowSelect = true;
if (this.Items.Count > 0)
this.Items.Clear();
this.BeginUpdate();
int i = 0;
foreach (T item in containerItems)
{
// do something
}
this.EndUpdate();
}
The parameter containerItems can have many items since I'm using generics. But I get stuck in the foreach loop. How do I access the values in containerItems?
Do I have to use reflection on each instance of T in the foreach loop? I think I do to retrieve the property name. But once I have the property name of the type T, how do I retrieve the value?
The most common way of doing this (with winforms) is via TypeDescriptor; this allow you to use things DataTable the same as classes; the "full" pattern is quite complex (and involves checking for IListSource, ITypedList, etc; however, the short version is; to get the available properties:
PropertyDescriptorCollection props = TypeDescriptor.GetProperties(typeof(T));
To get a named property:
PropertDescriptor prop = props[propName];
To get a value for an instance (sourceObject):
object val = prop.GetValue(sourceObject);
To render a value as a string (using the designated converter):
string s = prop.Converter.ConvertToString(val);
You could limit T to an interface, and use that interface in the iteration.
What does T represent ?
Like it is now, it is a generic type and it can be ... anything.
So, what I would do, is create an interface IListViewBindable or something like that. That interface could then have a method 'CreateListViewItem' for instance.
Then, I would change the method, so that a constraint is applied to your type-parameter T, saying that T should implement IListViewBindable, like this:
public void BindDataToListView<T>( List<T> containerItems ) where T : IListViewBindable
{}
In your BindDataToListView method, you could then do this:
foreach( T item in containerItems )
{
this.Items.Add (item.CreateListViewItem());
}
If the items in the list are of totally unconstrained type, then you can treat them as simply of type object. You call GetType() to get the type of the object. On that you can call GetProperties() to get an array of PropertyInfo objects. And on those you can call GetValue() to retrieve the value of the property.
If you already know the name of a property, just call GetProperty() to retrieve it:
string valueAsString = item.GetType().GetProperty("Something")
.GetValue(item, null).ToString();
I don't completely understand what you're asking, but I think that this will point you in the right direction. Please ask for clarification if it looks like it can help and it's unclear.
You can access a given property of an object using reflection via
object o;
PropertyInfo info = o.GetType().GetProperty().GetProperty("NameOfPropertyIWant");
and you can get the value via
object value = info.GetValue(o, null);
Now, if you're going to be accessing a property of the same name on objects of various types, you should consider adding an interface
public interface IHasThePropertyIWant {
object NameOfPropertyIWant { get; }
}
Then you can enforce this via
void BindDataToListView(List<T> containerItems) where T : IHasThePropertyIWant
and use it in the look like so
foreach (T item in containerItems) {
object o = item.NameOfPropertyIWant;
// do something with o
}
ObjectListView uses reflection to do exactly what you are trying to do: populate a ListView using reflection. You could save yourself a lot of trouble by using it. It has already solved all the tricky problems you are going to encounter on this path.
If you really, really want to do it yourself, Marc's answer is (of course) completely correct.
I am filling items to my ComboBox from a XML file using a DataTable. Currently I have it set so that one column is ComboBox's displaymember and another is it's value member. However this may not always work for me, since I have to set the selectedItem parameter, and value member may not be unique.
I don't know if there is a duplicate of the value member in the table or not, so my idea was that I would put entire DataRow as the value member of the ComboBox and then use ComboBox.SelectedITem = (DataRow)some_data_row; for selecting, and it would always select the right ComboBox object.
How would I accomplish this? IS there a better way of doing this? I'm open to suggestions, however it is very important that I can get to both, display member and value member.
Thank you for your help!
EDIT: Maybe I wasn't clear enough before, however while I am asking if this is the best approach here, I am also asking how to do this. If I don't set the valuemember parameter, the SelectedItem is of DataRowView type... Please note, that I want to use the selectedValue parameter to select items from ComboBox, and if I try to do that without explicitly setting the value member an exception is thrown.
If you bind a ListBox to a DataTable, you're actually binding it to a DataView that represents that DataTable (DataTable implements IListSource, and that returns a DataView). You can't directly set SelectedItem to a DataRow instance, you have to set it to a DataRowView instance. Unfortunately there's no easy way to obtain a DataRowView from a DataRow.
You would do better to just do all of your interactions through a DataRowView. This will allow you to set SelectedItem explicitly.
You cannot use the SelectedValue property, you must use SelectedItem for this.
First of all thank you Adam Robinson, I'm sure your answer was correct, but it just wasn't what I wanted to hear. I solved my problem in a different way and I think it may be useful to someone else, so I am posting it here.
What I did was I created a new class, in my case I named it ListObject, which had a property DataRow (as you will see later it works for other types too, I just used this since this is what I actually wanted as my Item value property). It also overrides methods:
String ToString()
bool Equals(object obj)
int GetHashCode() --is not needed in my case, however Visual Studio
warns you it should be overridden.
The idea was that I could fill ComboBox.Items collections with objects of my own class, display a custom string (if I had not worked it out like this, my next question on Stack overflow would probably be about customizing DisplayMembers when reading items from a DataRow) and compare only one class's item (in my case DataRow).
So here is the code and it works great (at least for what I wanted to do with it).
public class ListObject
{
public DataRow element;
public String DisplayObject = null;
public ListObject(DataRow dr)
{
element = dr;
}
public ListObject(DataRow dr, String dspObject)
{
element = dr;
DisplayObject = dspObject;
}
public override String ToString()
{
if (DisplayObject == null) throw new Exception("DisplayObject property was not set.");
return element[DisplayObject].ToString();
}
public override bool Equals(object obj)
{
if (obj.GetType() == typeof(ListObject))
return Equals(((ListObject)obj).element, this.element);
else return base.Equals(obj);
}
public override int GetHashCode()
{
return base.GetHashCode();
}
}
In my case it works great since I can just fill the ComboBox's with a foreach statement:
dtUsers.ReadXml(Program.Settings.xmlInputUsers);
foreach(DataRow dr in dtUsers.Rows)
{
cmbUser.Items.Add(new ListObject(dr, "Name"));
}
And when I get the DataRow I want selected I just do this:
cmbUser.SelectedItem = new ListObject(dlg.SelectedDataRow);
Where I don't have to worry about the DisplayMember etc, because only DataRow's will be compared, and your display parameters will still be set from when you filled ComboBox.Items collection. Also since toString method is overridden you can really customize your output.
Creating this class was only possible because of msdn article on ComboBox.SelectedItem Property in which it was noted, that SelectedItem property works using the IndexOf method. This method uses the Equals method to determine equality.
This is the most simple way to get DataTable to a combobox
private void load() {
DataTable dt = // get data from DB
comboBox1.ValueMember = null; // allows you to get all fields in the obj to combobox
comboBox1.DisplayMember = "ccType";//label displayed from dt
comboBox1.DataSource = dt;
}
//to test
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
DataRowView current = (DataRowView)comboBox1.SelectedValue;
string drs = current.Row["ID"].ToString();
}