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SnapLine Class

SnapLine Class

Represents the horizontal and vertical line segments that are dynamically created in the user interface (UI) to assist in the design-time layout of controls in a container. This class cannot be inherited.


Namespace:  System.Windows.Forms.Design.Behavior
Assembly:  System.Design (in System.Design.dll)

public sealed class SnapLine

The SnapLine type exposes the following members.

Public methodSnapLine(SnapLineType, Int32)Initializes a new instance of the SnapLine class using the specified snapline type and offset.
Public methodSnapLine(SnapLineType, Int32, String)Initializes a new instance of the SnapLine class using the specified snapline type, offset, and filter name.
Public methodSnapLine(SnapLineType, Int32, SnapLinePriority)Initializes a new instance of the SnapLine class using the specified snapline type, offset, and priority.
Public methodSnapLine(SnapLineType, Int32, String, SnapLinePriority)Initializes a new instance of the SnapLine class using the specified snapline type, offset, filter name, and priority.

Public propertyFilterGets the programmer-defined filter category associated with this snapline.
Public propertyIsHorizontalGets a value indicating whether the snapline has a horizontal orientation.
Public propertyIsVerticalGets a value indicating whether the snapline has a vertical orientation.
Public propertyOffsetGets the number of pixels that the snapline is offset from the origin of the associated control.
Public propertyPriorityGets a value indicating the relative importance of the snapline.
Public propertySnapLineTypeGets the type of a snapline, which indicates the general location and orientation.

Public methodAdjustOffsetAdjusts the Offset property of the snapline.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodStatic memberShouldSnapReturns a value indicating whether the specified SnapLine should snap to another SnapLine.
Public methodToStringReturns a string representation of the current snapline. (Overrides Object.ToString().)

The following table lists the common modes that visual design tools support to assist you with positioning and sizing controls on a design surface.




Enables you to freely lay out controls.


Displays a static overlaid grid that assists you in laying out controls.


Displays guide lines that assist you in laying out the container's controls relative to each other. Snaplines originate from controls and their container.

The SnapLine class and related types help support the Snapline mode.

Snaplines are generated dynamically and automatically as a control edge moves near another control or near the boundaries of its container. This can occur when a control is added from the toolbox, or moved or resized by mouse operations or keyboard commands. Controls typically have both horizontal and vertical snaplines defined; for rectangular controls, these typically extend from all four edges.

The SnapLine class uses only a few properties to describe each snapline, as shown in the following table.




Specifies the location and direction of the line with respect to its associated control. Typically, only snaplines of similar types will auto-align to each other.


Specifies the distance in pixels from the origin, which is the upper-left corner of the control, to where the snapline starts.


Specifies the relative importance of the snapline. During any given layout decision point, only the snaplines that are active and have the highest priority are displayed.


Defines custom categories of snaplines. This is an optional string.

IsHorizontal and IsVertical

Indicates whether a snapline has horizontal or vertical orientation, respectively.

The ControlDesigner class stores snaplines for its corresponding control type in the SnapLines property. This base class handling of snaplines will suffice for the majority of controls, as it defines the Left, Right, Top, and Bottom snaplines, which are aligned along the edges of the control. When you are developing a custom control, if this default organization does not suffice, override the SnapLines property of the class derived from ControlDesigner. For example, you may want to align the horizontal snaplines of text-based controls, such as labels, with the top and base lines of the text (instead of the top and bottom edges of the control).

The SnapLineType class cannot be derived from.

There is extensive support for this feature in Visual Studio, see Walkthrough: Arranging Controls on Windows Forms Using Snaplines.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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