设计人员必须创建......的一个实例，因为该类型被声明为抽象

Question

Visual Studio抱怨：警告1设计人员必须创建一个类型为'RentalEase.CustomBindingNavForm'的实例，但它不能因为该类型被声明为抽象。

Visual Studio不会让我访问窗体的Designer。该类已经实现了CustomBindingNavForm中的所有抽象方法。 CustomBindingNavForm提供了一些具体和抽象的函数。

有没有办法解决这个问题？

这里是类：

public abstract class CustomBindingNavForm : SingleInstanceForm {  

     //Flags for managing BindingSource 
     protected bool isNew = false; 
     protected bool isUpdating = false; 

     /// <summary> 
     /// This is so that when a new item is added, it sets isNew and firstPass to true. The Position Changed Event will look for 
     /// firstPass and if it is true set it to false. Then on the next pass, it will see it's false and set isNew to false. 
     /// This is needed because the Position Changed Event will fire when a new item is added. 
     /// </summary> 
     protected bool firstPass = false; 


     protected abstract bool validateInput(); 
     protected abstract void saveToDatabase(); 


     //manipulating binding 
     protected abstract void bindingSourceCancelResetCurrent(); 
     protected abstract void bindingSourceRemoveCurrent(); 
     protected abstract void bindingSourceMoveFirst(); 
     protected abstract void bindingSourceMoveNext(); 
     protected abstract void bindingSourceMoveLast(); 
     protected abstract void bindingSourceMovePrevious(); 
     protected abstract void bindingSourceAddNew(); 

     public void bindingNavigatorMovePreviousItem_Click(object sender, EventArgs e) { 
      if (validateInput()) { 
       bindingSourceMovePrevious(); 
      } else { 
       DialogResult cont = MessageBox.Show(null, "There are errors in your data. Click Cancel to go back and fix them, or ok to continue. If you continue, changes will not be saved.", "Continue?", MessageBoxButtons.OKCancel, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); 
       if (cont == DialogResult.OK) { 
        if (isNew) { 
         bindingSourceRemoveCurrent(); 
         isNew = false; 
        } else { 
         bindingSourceCancelResetCurrent(); 
         bindingSourceMovePrevious(); 
        } 
       } 
      } 
     } 

     public void bindingNavigatorAddNewItem_Click(object sender, EventArgs e) { 
      if (validateInput()) { 
       saveToDatabase(); 
       bool temp = isUpdating; 
       isUpdating = true; 
       bindingSourceAddNew(); 
       isUpdating = temp; 

       isNew = true; 
       firstPass = true; 
      } else { 
       DialogResult cont = MessageBox.Show(null, "There are errors in your data. Click Cancel to go back and fix them, or ok to continue. If you continue, changes will not be saved.", "Continue?", MessageBoxButtons.OKCancel, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); 
       if (cont == DialogResult.OK) { 

        if (isNew) { 
         bindingSourceRemoveCurrent(); 
         isNew = false; 
        } else { 
         bindingSourceCancelResetCurrent(); 
        } 

        bool temp = isUpdating; 
        isUpdating = true; 
        bindingSourceAddNew(); 
        isUpdating = temp; 

        isNew = true; 
        firstPass = true; 
       } 
      } 
     } 

     public void bindingNavigatorMoveFirstItem_Click(object sender, EventArgs e) { 
      if (validateInput()) { 
       bindingSourceMoveFirst(); 
      } else { 
       DialogResult cont = MessageBox.Show(null, "There are errors in your data. Click Cancel to go back and fix them, or ok to continue. If you continue, changes will not be saved.", "Continue?", MessageBoxButtons.OKCancel, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); 
       if (cont == DialogResult.OK) { 
        if (isNew) { 
         bindingSourceRemoveCurrent(); 
         isNew = false; 
        } else { 
         bindingSourceCancelResetCurrent(); 
        } 
        bindingSourceMoveFirst(); 
       } 
      } 
     } 

     public void bindingNavigatorMoveNextItem_Click(object sender, EventArgs e) { 
      if (validateInput()) { 
       bindingSourceMoveNext(); 
      } else { 
       DialogResult cont = MessageBox.Show(null, "There are errors in your data. Click Cancel to go back and fix them, or ok to continue. If you continue, changes will not be saved.", "Continue?", MessageBoxButtons.OKCancel, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); 
       if (cont == DialogResult.OK) { 
        if (isNew) { 
         bindingSourceRemoveCurrent(); 
         isNew = false; 
        } else { 
         bindingSourceCancelResetCurrent(); 
        } 
        bindingSourceMoveNext(); 
       } 
      } 
     } 
    } 

Answer 1

我还没有看到在城市的马铃薯（其下），但我和Smelch内容与解决方案上来。 Form本身继承自一个抽象类，所以他们不告诉你的是它的它的唯一的第一级继承，不能抽象，第二个下来可以。

从那里它简单地在中间有一个空的类，围绕形式声明包装#if debug，你很好去。只要确保在发布模式和调试模式下进行设计（这是非常典型的）。

您将在设计（调试）和构建（发布）时间获得完整的设计器支持和真正的抽象基类，因为每次它最终都会使用抽象基类。

The full explanation and answer is here