DataGridViewComboBoxColumn没有使用ValueMember [英] DataGridViewComboBoxColumn not taking ValueMember

问题描述

• 4 DataGridView


• 6个实体（2个映射表）


• 5数据关系

给你一个视觉图像，有1个大的雇主DGV（DataGridView），3个较小的根据雇主DGV选择的行更新。

3个较小的网格之一是一个非常简单的关系，没有映射表。

然而，另外2个显示使用其映射到的实体的formatedinfo的映射表行。那两个DGV只有1列，一个ComboBox与一个格式的字符串（覆盖 .ToString（）），（应该）有映射所指向的基础对象（EF将在接收到整个对象时相应地处理ID的设置）。但是，当我尝试添加一个新行时，它会说它无法将一个String转换为将对象名称放在这里。这导致我认为如果您没有设置ValueMember，组合框将尝试使用.ToString（）获取字符串表示。所以我试图通过向简单地返回自己的实体添加一个 Self 属性来绕过这种行为。没有成功，它仍然尝试将字符串转换到某处。

确切的错误（法语）是：

System.FormatException：将无法更改的'System.String'en'InvInformatique.logiciels'。

哪些传递到System.String到InvInformatique.logiciels的无效转换。

代码

i

bsEmployes.DataSource = iidb.employes;
bsMateriels.DataSource = iidb.materiels;
bsLogiciels.DataSource = iidb.logiciels;
bsLogicielEmployeMaps.DataSource = iidb.logiciel_employe_maps; //需要引发加载查询
bsAcces.DataSource = iidb.acces;
bsAccesEmployeMaps.DataSource = iidb.acces_employe_maps; //需要引发加载查询

dgvEmployes.AutoGenerateColumns = false;
dgvEmployes.Columns.AddRange（
new DataGridViewTextBoxColumn {Name = Nom，DataPropertyName =nom}，
new DataGridViewTextBoxColumn {Name =Département，DataPropertyName =departement}
）;
dgvEmployeMateriels.AutoGenerateColumns = false;
dgvEmployeMateriels.Columns.AddRange（
new DataGridViewTextBoxColumn {HeaderText =Nom，DataPropertyName =nom}，
new DataGridViewTextBoxColumn {HeaderText =Satisfaction，Name =satisfaction，DataPropertyName =满意}
）;
dgvEmployeAcces.AutoGenerateColumns = false;
dgvEmployeAcces.Columns.AddRange（
new DataGridViewComboBoxColumn {HeaderText =Accès，DataPropertyName =acces，DataSource = bsAcces}
）;
dgvEmployeLogiciel.AutoGenerateColumns = false;
dgvEmployeLogiciel.Columns.AddRange（
new DataGridViewComboBoxColumn {HeaderText =Logiciels，DataPropertyName =logiciels，DataSource = bsLogiciels}
）;

dgvEmployes.DataSource = bsEmployes;
dgvEmployeMateriels.DataBindings.Add（new Binding（DataSource，bsEmployes，materiels））;
dgvEmployeLogiciel.DataBindings.Add（new Binding（DataSource，bsEmployes，logiciel_employe_maps））;
dgvEmployeAcces.DataBindings.Add（new Binding（DataSource，bsEmployes，acces_employe_maps））;

数据库

 雇用
  - > id 
  - > nom 
  - >离开
 
加入
  - > id 
  - > nom 
  - > description 
 
 Logiciel 
  - > id 
  - > nom 
 
 Materiel 
  - > id 
  - > employe_id 
  - > nom 
  - > description 
 
 Acces_Employe_Maps 
  - > ; id 
  - > acces_id 
  - > employe_id 
 
 Logiciel_Employe_Maps 
  - > id 
  - > logiciel_id 
  - > employe_id 
  

数据库关系

 雇用<  - > Logiciel_Employe_Maps<  - > Logiciels 
雇用<  - > Acces_Employe_Maps<  - > Acces 
雇用 - >物品
  

解决方案

好的，DataGridViews不喜欢使用ToString （）获取一个DisplayMember。当我保持DisplayMember为空或使用我的自我属性时，它会将ValueMember错误。

设置 DisplayMember =nom，ValueMember =Self 完美工作。

修改

工作：

添加到EF部分类：

  public string FormatedName {get {return this.ToString（）; }} 
  

更改列定义：

  DisplayMember =FormatedName，ValueMember =Self
  

I have a Many to Many mixed with some Master-Detail DataGrid setup.

• 4 DataGridView
• 6 Entities (2 mapping tables)
• 5 Data relations

To give you a visual image, there is 1 big Employe DGV (DataGridView), and 3 smaller ones which updates depending on the Employe DGV selected row.

One of the 3 smaller grid is a really simple relation without a mapping table.

The other 2, however, displays a mapping table rows that uses formatedinfo of the entity it is mapping to. Those 2 DGV only have 1 column, a ComboBox with a formated string (overriden .ToString()) which (should) have the underlying object that the mapping is pointing to (EF will handle setting the ID accordingly when receiving the entire object). However, when I try to add a new rows, it will say it is unable to convert a String to a Put Object Name Here. This led me to think that if you did not set a ValueMember, the combobox would try to get a string representation using .ToString(). So I attempted to bypass that behavior by adding a Self property to the entity which simply returns himself. No success, it is still trying to convert a string somewhere.

The exact error (in french) is:

System.FormatException: Cast non valide de 'System.String' en 'InvInformatique.logiciels'.

Which traducts to "Invalid cast from System.String to InvInformatique.logiciels.

Code

InventaireInformatiqueEntities iidb = new InventaireInformatiqueEntities();

bsEmployes.DataSource = iidb.employes;
bsMateriels.DataSource = iidb.materiels;
bsLogiciels.DataSource = iidb.logiciels;
bsLogicielEmployeMaps.DataSource = iidb.logiciel_employe_maps; // Needed to provoke the load query
bsAcces.DataSource = iidb.acces;
bsAccesEmployeMaps.DataSource = iidb.acces_employe_maps; // Needed to provoke the load query

dgvEmployes.AutoGenerateColumns = false;
dgvEmployes.Columns.AddRange(
    new DataGridViewTextBoxColumn { Name = "Nom", DataPropertyName = "nom" },
    new DataGridViewTextBoxColumn { Name = "Département", DataPropertyName = "departement" }
);
dgvEmployeMateriels.AutoGenerateColumns = false;
dgvEmployeMateriels.Columns.AddRange(
    new DataGridViewTextBoxColumn { HeaderText = "Nom", DataPropertyName = "nom" },
    new DataGridViewTextBoxColumn { HeaderText = "Satisfaction", Name = "satisfaction", DataPropertyName = "satisfaction" }
);
dgvEmployeAcces.AutoGenerateColumns = false;
dgvEmployeAcces.Columns.AddRange(
    new DataGridViewComboBoxColumn { HeaderText = "Accès", DataPropertyName = "acces", DataSource = bsAcces }
);
dgvEmployeLogiciel.AutoGenerateColumns = false;
dgvEmployeLogiciel.Columns.AddRange(
    new DataGridViewComboBoxColumn { HeaderText = "Logiciels", DataPropertyName = "logiciels", DataSource = bsLogiciels }
);

dgvEmployes.DataSource = bsEmployes;
dgvEmployeMateriels.DataBindings.Add(new Binding("DataSource", bsEmployes, "materiels"));
dgvEmployeLogiciel.DataBindings.Add(new Binding("DataSource", bsEmployes, "logiciel_employe_maps"));
dgvEmployeAcces.DataBindings.Add(new Binding("DataSource", bsEmployes, "acces_employe_maps"));

Database

Employes
->id
->nom
->departement

Acces
->id
->nom
->description

Logiciel
->id
->nom

Materiel
->id
->employe_id
->nom
->description

Acces_Employe_Maps
->id
->acces_id
->employe_id

Logiciel_Employe_Maps
->id
->logiciel_id
->employe_id

Database relations

Employes <-> Logiciel_Employe_Maps <-> Logiciels
Employes <-> Acces_Employe_Maps <-> Acces
Employes -> Materiel

解决方案

Ok so, DataGridViews don't like using ToString() to get a DisplayMember. When I keep DisplayMember empty or use my Self property, it bugs out the ValueMember.

Setting DisplayMember = "nom", ValueMember="Self" worked perfectly.

Edit

This also worked:

Add to EF partial class:

public string FormatedName { get { return this.ToString(); } }

Change in column definition:

DisplayMember = "FormatedName", ValueMember = "Self"

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