Error: Send transaction failed: Invalid address. if you use injected provider, please check it is properly unlocked

Question

I have written my first sample contract. It compiled successfully but when I am trying to run this, it is giving me an error as:

Send transaction failed: Invalid address. if you use injected provider, please check it is properly unlocked.

Code is as follows:

pragma solidity ^0.4.22;

contract Myfirstcontract 
{
    string private name;
    uint private age;

    function setName (string newName)
    {
        name = newName;
    }

    function getName () returns (string)
    {
        return name;
    }

    function setAge (uint newAge)
    {
        age = newAge;
    }

    function getAge () returns (uint)
    {
        return age;
    } 


}

Please suggest.

Answer 1

The newer MetaMask versions sometimes have this error if you are in "Privacy Mode" To resolve it

1. Go to Metamask
2. Select Settings
3. Go to Security and Privacy
4. Turn off Privacy Mode

When Privacy Mode is on, it doesn't allow remix to read your accounts from injected web3

Answer 2

As it says "unlock the injected provider", it means you have to unlock the personal account that is associated with your network.

personal.unlockAccount(eth.accounts[0])
Unlock account 0xee3f0cd76f27d8cff90e23e53e82d461b6e5731e
Passphrase: 
true