當創建一個新項目時,我希望這個項目從下拉菜單中變爲可用。我創建,工作的第一個項目,作爲菜單項以及下拉項目放置,但是當我嘗試添加下一個下拉項目時,它會崩潰並告訴我「對象引用未設置爲對象的實例」。c#:我如何在運行時添加下拉菜單項
此行創建異常: ProjectToolStripMenuItem.DropDownItems.Add(newproject);
ArrayList projects = new ArrayList();
private void toolStripMenuItem1_Click(object sender, EventArgs e)
{
Project moldProject = new Project();
moldProject.ProjectName = "unnamed";
ToolStripMenuItem ProjectToolStripMenuItem = null;
if (projects.Count == 0)
{
ProjectToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
ProjectToolStripMenuItem.Name = "projectToolStripMenuItem";
ProjectToolStripMenuItem.Size = new System.Drawing.Size(44, 20);
ProjectToolStripMenuItem.Text = "unnamed*";
this.menuStrip1.Items.Add(ProjectToolStripMenuItem);
}
ToolStripMenuItem newproject = new System.Windows.Forms.ToolStripMenuItem();
string name = "aboutToolStripMenuItem" + (projects.Count + 1).ToString();
newproject.Name = name;
newproject.Size = new System.Drawing.Size(211, 22);
newproject.Text = "unnamed*";
ProjectToolStripMenuItem.DropDownItems.Add(newproject);
projects.Add(moldProject);
}