C# what is the point or benefit of an indexer?

Question

Doing some code reading and stumbled upon this snippet that I haven\'t seen before:

public SomeClass {
  public someInterface this[String strParameter] {
            


        

Answer 1

In my opinion, it's just a syntax convenience. Where would you NOT use it:

public SomeClass {
  private int[] nums;
  public GetVal this[int ind] {
    get {
      return nums[ind]; // this is pointless since array is already indexed
    }
  }
}

Where would you benefit from it:

public Matrix {
  private Dictionary matrixData; // Matrix indecies, value
  public double this[int row, int col] {
    get {
      return matrixData[string.Format("{0},{1}", row, col)];
    }
  }
}

As you can see, for some reason, your data is a Dictionary indexed with a string key and you wish to call this with two integer indecies and still do not want to change your data type:

Matrix m = new Matrix();
...
Console.WriteLine( m[1,2] );