c# - NullReferenceException 将输入发送到 TextBox

Question

我正在尝试将一个字符串从 form2 发送到 form3 以使用信息预加载表单。我在 form3 上调用一个方法，接受启动 linq 查询的字符串，以在表单上设置控件。我得到一个 NullReferenceException was unhandled in the first foreach on recipeNameTextBox.Text = a.RecipeName;我可以看到查询已运行并且信息位于 a.RecipName 中。我想我可能会收到此错误，因为尚未绘制控件。任何想法如何解决这个问题？ Form2 代码在这里:

 private void updateButton_Click(object sender, EventArgs e)
 {
     Form3 Frm3 = new Form3();
     Frm3.Show();

     this.Hide();
     Frm3.takeInputFromForm2(recipeLabel.Text);
}

此处为 form3 代码:

 public void takeInputFromForm2(string incommingUpdateRecipe)
 {
     Query updateRecipe = new Query();
     IEnumerable<Recipe> newrecipe = updateRecipe.getRecipeInfo(incommingUpdateRecipe);
     foreach (var a in newrecipe)
     {
         recipeNameTextBox.Text = a.RecipeName;
         nationalityTextBox.Text = a.Nationality;
         eventTextBox.Text = a.Event;
         sourceTextBox.Text = a.Source;
         typeTextBox.Text = a.Type;
         ServingsTextBox.Text = a.Servings;
    }
    foreach (var b in newrecipe)
    {
        userRatingTextBox.Text = Convert.ToString(b.UserRating);
        familyRatingTextBox.Text = Convert.ToString(b.FamilyRating);
        healthRatingTextBox.Text = Convert.ToString(b.HealthRating);
        easeOfCookingTextBox.Text = Convert.ToString(b.CookingTime);
        cookingTimeTextBox.Text = Convert.ToString(b.CookingTime);
    }
    foreach (var c in newrecipe)
    {
        ingredientComboBox.Items.Add(c.RecipeIngredient);
    }
}

Answer 1

您可能缺少 Form3 构造函数中的 InitializeComponent。