How to use the GetLowerBound method of array class in C#

The GetLowerBound() method of the Array class in C# returns the lower bound of the specified dimension in an array. For most arrays in C#, the lower bound is typically 0, but this method becomes useful when working with arrays that have custom bounds or multi-dimensional arrays.

Syntax

Following is the syntax for the GetLowerBound() method −

public int GetLowerBound(int dimension);

Parameters

• dimension − A zero-based dimension of the array whose lower bound needs to be found.

Return Value

Returns an integer representing the lower bound of the specified dimension.

Using GetLowerBound with Single-Dimensional Arrays

For standard single-dimensional arrays, the lower bound is always 0 −

using System;

class Program {
    static void Main(string[] args) {
        Array arr = Array.CreateInstance(typeof(string), 3);
        arr.SetValue("Car", 0);
        arr.SetValue("Truck", 1);
        arr.SetValue("Motorbike", 2);
        
        Console.WriteLine("Lower Bound: {0}", arr.GetLowerBound(0));
        Console.WriteLine("Upper Bound: {0}", arr.GetUpperBound(0));
        Console.WriteLine("Array Length: {0}", arr.Length);
    }
}

The output of the above code is −

Lower Bound: 0
Upper Bound: 2
Array Length: 3

Using GetLowerBound with Multi-Dimensional Arrays

The method is more useful with multi-dimensional arrays where you need to check bounds for different dimensions −

using System;

class Program {
    static void Main(string[] args) {
        int[,] matrix = new int[3, 4] {
            {1, 2, 3, 4},
            {5, 6, 7, 8},
            {9, 10, 11, 12}
        };
        
        Console.WriteLine("Dimension 0 - Lower Bound: {0}, Upper Bound: {1}", 
                         matrix.GetLowerBound(0), matrix.GetUpperBound(0));
        Console.WriteLine("Dimension 1 - Lower Bound: {0}, Upper Bound: {1}", 
                         matrix.GetLowerBound(1), matrix.GetUpperBound(1));
        
        Console.WriteLine("Array Rank (dimensions): {0}", matrix.Rank);
    }
}

The output of the above code is −

Dimension 0 - Lower Bound: 0, Upper Bound: 2
Dimension 1 - Lower Bound: 0, Upper Bound: 3
Array Rank (dimensions): 2

Using GetLowerBound with Arrays Having Custom Bounds

You can create arrays with custom lower bounds using Array.CreateInstance() −

using System;

class Program {
    static void Main(string[] args) {
        // Create array with custom bounds: starts at index 5, length 3
        Array customArray = Array.CreateInstance(typeof(int), new int[] {3}, new int[] {5});
        
        customArray.SetValue(100, 5);
        customArray.SetValue(200, 6);
        customArray.SetValue(300, 7);
        
        Console.WriteLine("Lower Bound: {0}", customArray.GetLowerBound(0));
        Console.WriteLine("Upper Bound: {0}", customArray.GetUpperBound(0));
        Console.WriteLine("Length: {0}", customArray.Length);
        
        // Display values
        for (int i = customArray.GetLowerBound(0); i <= customArray.GetUpperBound(0); i++) {
            Console.WriteLine("Index {0}: {1}", i, customArray.GetValue(i));
        }
    }
}

The output of the above code is −

Lower Bound: 5
Upper Bound: 7
Length: 3
Index 5: 100
Index 6: 200
Index 7: 300

Comparison with Related Methods

Conclusion

The GetLowerBound() method is essential for determining the starting index of array dimensions, especially when working with multi-dimensional arrays or arrays with custom bounds. It helps write robust code that can handle arrays with varying index ranges safely.