Summary of selectedvalue settings in ComboBox in winform (selectedvalue = NULL solution)

In practice, we found that the selectedindex value can be used to obtain selectedvalue when ComboBox is automatically selected; The selectedtext value can be used to leave selectedvalue empty when ComboBox is automatically selected.

That is

This. combobox1.selectedindex = This. combobox1.findstring (room );

In this way, the combobox1.selectedvalue value is obtained.

This. combobox1.selectedtext = room;

In this way, the value of combobox1.selectedvalue is null.

 

The content of the post is as follows:

Recently, when processing a ComboBox value set in a winform in the project, it is strange that when an object matches an object in the datasource set of ComboBox, when selectedvalue is set, the value of selectedvalue is null.

If you use dateset to bind data, selectedvalue returns NULL or datarowview.

 

After repeated practices, we found that the following methods can be used:

Private void setvaluebyitem ()
{
Area A = new area ();
A. area_id = "8 ";
A. area_name = "8th ";
Cblist. selecteditem = ac. findall (delegate (area AR) {return ar. area_id = A. area_id;}) [0];
Lbresult. Text = cblist. selecteditem. GetType (). tostring () + ":" + cblist. selectedvalue. tostring ();
} Two other setting methods: Private void setvaluebyvalue ()
{
Area A = new area ();
A. area_id = "8 ";
A. area_name = "8th ";
Cblist. selectedvalue = A. area_id;
Lbresult. Text = cblist. selectedvalue. GetType (). tostring () + ":" + cblist. selectedvalue. tostring ();
} Complete code:

Using system; using system. collections. generic; using system. componentmodel; using system. data; using system. drawing; using system. text; using system. windows. forms; namespace winformcombobox {public partial class frmmain: FORM {public frmmain () {initializecomponent () ;}# region members arealists AC; Public arealists gettestarea () {arealists Al = new arealists (); For (INT I = 1; I <11; I ++) {Area A = new area ();. area_id = I. tostring ();. area_name = "no" + I. tostring () + "name"; Al. add (a) ;}return Al ;}# endregion # region events private void frmmain_load (Object sender, eventargs e) {AC = gettestarea (); cblist. datasource = ac; cblist. displaymember = "area_name"; cblist. valuemember = "area_id";} private void btnsetcombobox_click (Object sender, eventargs e) {// setvalue0 (); // setvaluebyvalue (); // setvaluebyitem (); setvaluebytext () ;}# endregion # Region Methods private void setvalue0 () {Area A = new area ();. area_id = "8";. area_name = "8th"; cblist. datasource = gettestarea (); cblist. displaymember = "area_name"; cblist. valuemember = "area_id"; cblist. selectedvalue =. area_id; lbresult. TEXT = cblist. selectedvalue. tostring ();} private void setvaluebyvalue () {Area A = new area ();. area_id = "8";. area_name = "8th"; cblist. selectedvalue =. area_id; lbresult. TEXT = cblist. selectedvalue. getType (). tostring () + ":" + cblist. selectedvalue. tostring ();} private void setvaluebyitem () {Area A = new area ();. area_id = "8";. area_name = "8th"; cblist. selecteditem = ac. findall (delegate (area AR) {return ar. area_id =. area_id;}) [0]; lbresult. TEXT = cblist. selecteditem. getType (). tostring () + ":" + cblist. selectedvalue. tostring ();} private void setvaluebytext () {Area A = new area ();. area_id = "8";. area_name = "8th"; cblist. selectedindex = cblist. findstring (. area_name); lbresult. TEXT = cblist. selectedvalue. getType (). tostring () + ":" + cblist. selectedvalue. tostring () ;}# endregion }} using system; using system. collections. generic; using system. text; namespace winformcombobox {# region area public class area {private string m_area_id; Public String area_id {get {return m_area_id;} set {m_area_id = value;} private string m_area_name; public String area_name {get {return m_area_name;} set {m_area_name = value;} private double m_area_order; Public double area_order {get {return m_area_order ;} set {m_area_order = value ;}}# endregion [serializable] public class arealists: List <area> {private int _ maxitems = 0; Public int maxitems {get {return this. _ maxitems;} set {This. _ maxitems = value ;}}}}