A control is dynamically created through reflection. How can I use the name of the control to get the control through the emission function?

This article from: http://topic.csdn.net/t/20060712/02/4874504.html

 

The following code dynamically creates a control on the form:

String assname = typeof (system. Windows. Forms. Form). assemblyqualifiedname;

String assinfo = assemblyqualifiedname. substring (assemblyqualifiedname. indexof (","));

Type T = system. type. GetType ("system. Windows. forms." + ctrltype + assinfo, true );

Control CTRL = (Control) activator. createinstance (t );

This. Controls. Add (CTRL );

Then, use the following code to obtain the control again with a string:

Type T = This. GetType ();

Fieldinfo = T. getfield (ctrlname, bindingflags. Public | bindingflags. nonpublic | bindingflags. instance | bindingflags );

But I found that fieldinfo is null... why? Then how can we obtain the control based on the string?

 

Reply: 03:14:49

Are you sure ctrlname is a field of the current object? If it is an object in controls, you need to obtain the CONTROLS attribute, and then find the required control in the loop.

 

Reply: 09:01:46

Object o = form name. GetType (). GetField (Control name, System. Reflection. BindingFlags. Instance | System. Reflection. BindingFlags. NonPublic). GetValue (form name ); If (o! = Null) { CheckBox dtp = (CheckBox) o; ....

 

 

Reply: 09:25:21

Control control = this. Controls [Control name]

 

Reply: 09:47:56

To Saucer: If the control is dragged from the toolbox in Visual Studio to Form, my code can run normally. Now I am based on an XML content, after dynamically creating controls on the Form, my code cannot run successfully... To Knight94: I have a CreateControls () function to read the XML, and then dynamically create an object on the form. After the function is executed, write "Type t = this. getType.

 

Reply: 09:53:47

To stlwj: Now I have used the Form to dynamically create a TextBox: textName, run Object o = this. GetType (). GetField ("textName", System. Reflection. BindingFlags. Instance | System. Reflection. BindingFlags. NonPublic). GetValue (this ); Exception: System. NullReferenceException: the object reference is not set to the instance of the object.

 

Reply: 09:56:26

Is it because all objects are dynamically created, so it cannot be obtained using Type. GetField? If so, what should I do to get the dynamically created object? Hope you can give me some advice!

 

Reply: 10:26:18

Create a dynamic object: First, read the name of the object to be created and its assembly path from the file. Assembly asm = Assembly. LoadFile (Assembly file path ); Object OBJ = ASM. createinstance ("Class Name", false, bindingflags. public | bindingflags. instance | bindingflags. createinstance, null, null); if the class requires a constructor, You need to initialize the constructor.

 

Reply: 10:29:06

Private void CreateControls (XmlNodeList _ xnl, Panel _ panel) { Foreach (XmlNode _ xn in _ xnl) { String ctrlType = (XmlElement) _ xn). GetAttribute ("type "); String assname = typeof (system. Windows. Forms. Form). assemblyqualifiedname; String assinfo = assname. substring (assemblyqualifiedname. indexof (",")); Type T = system. type. GetType ("system. Windows. forms." + ctrltype + assemblyinformation, true ); Control CTRL = (Control) activator. createinstance (t ); _ Panel. suspendlayout (); Ctrl. Location = new System. Drawing. Point (X, Y ); Ctrl. Name = _ xn ["Name"]. InnerText; Ctrl. Size = new System. Drawing. Size (Width], Height ); Ctrl. Text = _ xn ["Text"]. InnerText; Ctrl. Visible = bool. Parse (_ xn ["Visible"]. InnerText ); _ Panel. Controls. Add (ctrl ); _ Panel. ResumeLayout (); } } Private void SetControlsText (XmlNodeList xnl) { Foreach (XmlNode _ xn in xnl) { Type t = this. GetType (); FieldInfo fieldInfo = t. GetField (_ xn ["Control"]. InnerText, BindingFlags. Public | BindingFlags. NonPublic | BindingFlags. Instance | BindingFlags ); ... ... ... } } To Knight94: dynamically create controls and reuse types. getField () to obtain the control function. The program runs CreateControl () and SetControlText (), but fieldInfo is null at last... Why...

 

Reply: 10:33:01

The above program has a written mistake: In CreateControl (), String assName = typeof (System. Windows. Forms. Form). AssemblyQualifiedName; String assInfo = assName. Substring (assemblyQualifiedName. IndexOf (",")); Type t = System. Type. GetType ("System. Windows. Forms." + ctrlType + assemblyInformation, true ); It should be String assName = typeof (System. Windows. Forms. Form). AssemblyQualifiedName; String assInfo = assName. Substring (assName. IndexOf (",")); Type t = System. Type. GetType ("System. Windows. Forms." + ctrlType + assInfo, true );

 

Reply: 16:30:39

To, if I dynamically create a control in the form Load event, how can I operate the control in the remaining code? Do you know the name? If you know it, you can: Foreach (Control ctrl in this. Controls) { If (CTRL. Name = yourname) { // Get it } }

 

Reply: 16:36:29

Sample code as follows: Private control CTRL = NULL; Change Control CTRL = (Control) activator. createinstance (t ); With CTRL = (Control) activator. createinstance (t );

 

Reply: 10:02:31

Type t = this. GetType (); -- Type of the form Fieldinfo = T. getfield (ctrlname, bindingflags. Public | bindingflags. nonpublic | bindingflags. instance | bindingflags ); -- Getfield obtains the field of the Form class, and the Form class does not contain members named ctrlname. -- The value obtained here must be null.