Can i change the Texture of terrain

I think this would work..there are some things you would need to do to make it ok for your situation but this should be a good outline or start. If im wrong someone please correct me.

 var TerrainOne : Terrain;
 var TerrainTwo :Terrain;
 
 
 function Start () {
 Terrain = TerrainOne;
 }
 
 function Update () {
     if(!Input.GetButtonDown(TerrainTwo)){
     }
         if(Input.GetButtonDown(TerrainOne)){
     }
 }

 SplatPrototype[] splats = yourTerrainGameObjct.GetComponent<Terrain>().terrainData.splatPrototypes;
 
 for(int i=0;i<splats.Length;i++)
 {
    splats[i].texture = (Texture2D)yourTexture;
 }

so far i achive this my texture swap is working but i want the whole terrain texture to change at once and the scond function is not working i dnt knw thier are no errors in code but its not working texture swap is only working on the painted areas can i repaint the texture of the terrian throug scripting

here is my code

 using UnityEngine;
 using System.Collections;
 
 public class TerrainTextureChanger : MonoBehaviour {
 
  public Terrain terrain;
  public Texture2D MyTexture;
     void Update()
     {
         if (Input.GetKeyDown(KeyCode.Space))
         {
             //switch all painted in texture 1 to texture 2
             UpdateTerrainTexture(terrain.terrainData, 1, 2);
         }
         if (Input.GetKeyUp(KeyCode.Space))
         {
             //switch all painted in texture 2 to texture 1
             UpdateTerrainTexture(terrain.terrainData, 2, 1);
         }
         if (Input.GetKeyDown(KeyCode.LeftControl))
         {
             textureChange();
         }
     }
      void textureChange(){
         Debug.Log ("i am hapnig");
     SplatPrototype[] splats = terrain.GetComponent<Terrain>().terrainData.splatPrototypes;
      
     for(int i=0;i<splats.Length;i++)
     {
     splats[i].texture = MyTexture;
 //                (Texture2D)
     }
     }
     
     
     static void UpdateTerrainTexture(TerrainData terrainData, int textureNumberFrom, int textureNumberTo)
     {
         //get current paint mask
         float[, ,] alphas = terrainData.GetAlphamaps(0, 0, terrainData.alphamapWidth, terrainData.alphamapHeight);
         // make sure every grid on the terrain is modified
         Debug.Log (alphas);
         for (int i = 0; i < terrainData.alphamapWidth; i++)
         {
             for (int j = 0; j < terrainData.alphamapHeight; j++)
             {
                 //for each point of mask do:
                 //paint all from old texture to new texture (saving already painted in new texture)
                 alphas[i, j, textureNumberTo] = Mathf.Max(alphas[i, j, textureNumberFrom], alphas[i, j, textureNumberTo]);
                 //set old texture mask to zero
                 alphas[i, j, textureNumberFrom] = 0f;
             }
         }
         // apply the new alpha
         terrainData.SetAlphamaps(0, 0, alphas);
     }
 }