SQL Injection - How To Prevent It?

I am building my first ASP.Net app from scratch and while working on the DAL I came across the problem of SQL Injection. I searched on the web and read different articles but I am still unsure about the answer. My question is should I add
 
db.AddInParameter(dbCommand, "AvatarImageID", DbType.Int32, avatarImageID);
 
Add in Parameters to my C# code to avoid SQL Injection. What is the best practice. I am unclear if the stored procedure already helps me avoid SQl Injection or if I need the add in parameters in the C# methods to make it work. I need some help. Thanks, Newbie
 
My C# update method in the DAL (still working on the code)
 
private static bool Update(AvatarImageInfo avatarImage)
        {
            //Invoke a SQL command and return true if the update was successful.
            db.ExecuteNonQuery("syl_AvatarImageUpdate",
                avatarImage.AvatarImageID,
                avatarImage.DateAdded,
                avatarImage.ImageName,
                avatarImage.ImagePath,
                avatarImage.IsApproved);
 
            return true;
        }
 
 
I am using stored procedures to access the data in the database.
 
My update stored proc
 
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
 
ALTER PROCEDURE [dbo].[syl_AvatarImageUpdate]
      @AvatarImageID          int, 
      @DateAdded              datetime,  
      @ImageName              nvarchar(64),    
      @ImagePath              nvarchar(64),    
      @IsApproved             bit
AS
BEGIN
      -- SET NOCOUNT ON added to prevent extra result sets from
      -- interfering with SELECT statements.
      SET NOCOUNT ON;
      BEGIN TRY
            UPDATE      [syl_AvatarImages]
            SET
                        [DateAdded]       = @DateAdded,
                        [ImageName]       = @ImageName,
                        [ImagePath]       = @ImagePath,
                        [IsApproved]      = @IsApproved
            WHERE [AvatarImageID] = @AvatarImageID
            RETURN
      END TRY
      BEGIN CATCH
            --Execute LogError SP  
            EXECUTE [dbo].[syl_LogError];
            --Being in a Catch Block indicates failure.
            --Force RETURN to -1 for consistency (other return values are generated, such as -6).
            RETURN -1
      END CATCH
END