I want to find Early Start and EarlyFinish in CPM (Critical path method) can't anyone help

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C#

i am working on the windows app that calculate critical path i am just a beginner Programmer. my program need to import excel file and convert it to 2 datagridview and then i was unable to write the algorithm that calculate them andy one can help me ? here is my code

private List<int> Duration_Values = new List<int>(); // T 
private int Duration; // T
private string Predecessor;  
private List<string> Predecessor_Values = new List<string>();
private string Proj_name; 
private List<string> Proj_name_Values = new List<string>(); 
private int Earlystart;
private List<int> EarlyStart_value = new List<int>();
private List<string> Predecessor_Number = new List<string>();
private int FindES;
private List<int> FindES_Value = new List<int>();

// this is all what i create to use this 

for (int X = 0; X <= dataGridView1.RowCount - 1; X++) 
{

    Proj_name = Convert.ToString(dataGridView1.Rows[X].Cells[0].Value);

    Proj_name_Values.Add(Convert.ToString(Proj_name));
}
for (int X = 0; X <= dataGridView1.RowCount - 1; X++) 
{

    Duration = Convert.ToInt32(dataGridView1.Rows[X].Cells[1].Value);

    Duration_Values.Add(Convert.ToInt32(Duration));
}

for (int X = 0; X <= dataGridView1.RowCount - 1; X++) 
{

    Predecessor = Convert.ToString(dataGridView1.Rows[X].Cells[2].Value);

    String[] Word = Predecessor.Split(' ');

    Predecessor_Number.Add(Convert.ToString(Word.Length));

    Predecessor_Values.Add(Convert.ToString(Predecessor));
}

and this for looking up for the predecessor i can just set Earlystart if there isn't need any predecessor

for (int i = 0; i < Proj_name_Values.Count - 1; i++)
{
    if (Predecessor_Number[i] == "1")
    {
        if (Predecessor_Values[i] == "-")
        {
            Earlystart = 0;
            EarlyStart_value.Add(Convert.ToInt32(Earlystart));

        }
}

i have no clue in doing this anyone can help me ? Please T^T
PS: Sorry if i suck at English