Recursion, help finding the base case?

private void btnRepeat_Click(object sender, EventArgs e)
{
    

}

string Repeat(char c, int n)
{
    return string.Empty;

}

private void btnRepeat_Click(object sender, EventArgs e)
{
    

}

string Repeat(char c, int n)
{
    return string.Empty;

}

private void btnRepeat_Click(object sender, EventArgs e)
{
    

}

string Repeat(char c, int n)
{
    return string.Empty;

}

private void btnRepeat_Click(object sender, EventArgs e)
{
    

}

string Repeat(char c, int n)
{
    return string.Empty;

}

I think the idea is that if c is 1 letter, it is the base case and then after it increases. Not sure exactly how to implement it, very new to coding