In C#, when the property DropDownStyle of ComboBox is set to DropDownList, the text of ComboBox2 box is left-aligned by default.
Take ComboBox1 as an example to center the drop-down text and subscribe to events:
public Form2()
{
InitializeComponent();
comboBox1.DrawMode = DrawMode.OwnerDrawFixed;
comboBox1.DrawItem + = new DrawItemEventHandler(comboBox1_DrawItem);
}
What this code does is to set the drawing mode of a combo box control named comboBox2 to OwnerDrawFixed, and add an event handler named comboBox2_DrawItem to the DrawItem event of the control.
In C#, the ComboBox control has several drawing modes, including Normal, OwnerDrawFixed, OwnerDrawVariable, and Professional. In Normal mode, the ComboBox control uses the default drawing method to render its items. In the OwnerDrawFixed and OwnerDrawVariable modes, developers can customize the drawing method of the ComboBox control to better meet the needs of the application.
Event of DrawItem of ComboBox1:
private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
{
if (e. Index < 0)
{
return;
}
e.DrawBackground();
string text = comboBox1.GetItemText(comboBox1.Items[e.Index]);
SizeF textSize = e.Graphics.MeasureString(text, comboBox1.Font);
float left = (float)(e.Bounds.Width - textSize.Width) / 2;
float top = (float)(e.Bounds.Height - textSize.Height) / 2;
e.Graphics.DrawString(text, comboBox1.Font, Brushes.Black, e.Bounds.Left + left, e.Bounds.Top + top);
e.DrawFocusRectangle();
}
This code uses the DrawMode.OwnerDrawFixed property to customize how ComboBox1 is drawn. We then subscribed to the DrawItem event, which fires when each item is drawn. In the event handler, we first draw the background, then get the current item’s text and measure its size. Next, we calculate where the text should be drawn so that it is center-aligned. Finally, we draw the text into ComboBox1 using the Graphics.DrawString method.
The above method only centers the drop-down text, but cannot center the text of the ComboBox1 box, as shown in the figure:
To set the DropDownStyle property of ComboBox1 to center the text of the DropDownList and the text of the ComboBox1 text box, the following steps can be implemented:
- Open Visual Studio and open your C# project.
- Find the ComboBox1 control, double-click to open its properties window.
- Find the DropDownStyle property in the Properties window and set it to DropDownList.
- Find the DrawMode property in the Properties window and set it to OwnerDrawFixed.
- Find the ItemHeight property in the Properties window and set it to the height of ComboBox1. (This step can be ignored)
- Find the DrawItem event in the properties window, double-click to open its code editor.
- Add the following code in the code editor:
private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
{
if (e. Index < 0) return;
e.DrawBackground();
e.DrawFocusRectangle();
string text = comboBox1.GetItemText(comboBox1.Items[e.Index]);
using (StringFormat sf = new StringFormat())
{
sf.Alignment = StringAlignment. Center;
e.Graphics.DrawString(text, e.Font, Brushes.Black, e.Bounds, sf);
}
}
8. Save and run your program, the text of ComboBox1 should now be centered.
If you want the ComboBox1 drop-down box and text box to display colorless, you can add this line of code
e.Graphics.FillRectangle(Brushes.White, e.Bounds);
or
private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
{
e.DrawBackground();
if (e. Index >= 0)
{
string text = comboBox1.Items[e.Index].ToString();
using (StringFormat sf = new StringFormat())
{
sf.Alignment = StringAlignment. Center;
e.Graphics.DrawString(text, e.Font, Brushes.Black, e.Bounds, sf);
}
}
e.DrawFocusRectangle();
}
The function of this code is to center the text in the drop-down list in the drawing event of the ComboBox control. Specifically, it uses the StringFormat class to set the alignment of the text, and then uses the DrawString method of the Graphics class to draw the text at the specified position.
In the DrawItem event of ComboBox1, center the text of ComboBox1 and display the text in the center, as shown in the figure below:
If only the text of the ComboBox drop-down box is centered, the text in the ComboBox box remains unchanged on the left:
The ComboBox control is a commonly used drop-down list box control. By default, the text of the ComboBox control is center-aligned. If you want to center only the drop-down text of ComboBox1, but not the text of ComboBox1, you can do it through the following steps:
- Open Visual Studio and create a Windows Forms application.
- Add a ComboBox control on the form.
- In the property window of the ComboBox control, find the DropDownStyle property and set it to DropDown.
- In the Properties window of the ComboBox control, find the DrawMode property and set it to OwnerDrawFixed.
- In the event of the ComboBox control, add the following code:
private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
{
e.DrawBackground();
if (e. Index >= 0)
{
string text = comboBox1.Items[e.Index].ToString();
using (StringFormat sf = new StringFormat())
{
sf.Alignment = StringAlignment. Center;
e.Graphics.DrawString(text, e.Font, Brushes.Black, e.Bounds, sf);
}
}
e.DrawFocusRectangle();
}
Not centered by default, in the DrawItem event of ComboBox1:
e.DrawBackground();
if (e. Index >= 0)
{
StringFormat sf = new StringFormat();
sf.LineAlignment = StringAlignment.Center;
e.Graphics.DrawString(comboBox2.Items[e.Index].ToString(), e.Font, new SolidBrush(e.ForeColor), e.Bounds, sf);
}
The above method is just for reference, and the actual application can be modified according to the needs. If there is a better method, please add it!
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