EditorGUI.BeginChangeCheck

Description

Starts a new code block to check for GUI changes.

Use this in combination with EditorGUI.EndChangeCheck to create a code block that checks if the GUI state changed for just the controls contained in that block.
This method is different from GUI.changed, which returns true for any changes to the GUI state. BeginChangeCheck() limits the check to a specific set of controls.

using UnityEditor;

public class ExampleWindow : EditorWindow
{
    float sliderValue = 0;
    string labelText = "-";

    [MenuItem("Window/Example Window")]
    static void Init()
    {
        var example = (ExampleWindow)EditorWindow.GetWindow(typeof(ExampleWindow));
        example.Show();
    }

    void OnGUI()
    {
        EditorGUILayout.LabelField("New value", labelText);

        // Start a code block to check for GUI changes
        EditorGUI.BeginChangeCheck();

        sliderValue = EditorGUILayout.Slider(sliderValue, 0, 1);

        // End the code block and update the label if a change occurred
        if (EditorGUI.EndChangeCheck())
        {
            labelText = sliderValue.ToString();
        }
    }
}