"String or data would be truncated"

See more:

C#

SQL

Hello guys, I'm creating a software to help me out on my gym and I want to add a plan to a client, but when I add it it gives me this error "string or data would be truncated".


This is the code i actually have for the save button.

try
{
    if (txtMemberName.Text == "")
    {
        MessageBox.Show("Introduza os dados de cliente", "",
        MessageBoxButtons.OK, MessageBoxIcon.Warning);
        txtMemberName.Focus();
        return;
    }
    if (txtMonths.Text == "")
    {
        MessageBox.Show("Introduza o tempo de subscrição (meses)", "",
        MessageBoxButtons.OK, MessageBoxIcon.Warning);
        txtMonths.Focus();
        return;
    }
    if (cmbMembershipType.Text == "")
    {
        MessageBox.Show("Escolha o tipo de plano", "",
        MessageBoxButtons.OK, MessageBoxIcon.Warning);
        cmbMembershipType.Focus();
        return;
    }
    if (txtDiscountPer.Text == "")
    {
        MessageBox.Show("Introduza o desconto", "", MessageBoxButtons.OK, MessageBoxIcon.Warning);
        txtDiscountPer.Focus();
        return;
    }
    if (txtTotalPaid.Text == "")
    {
        MessageBox.Show("Introduza o valor pago", "",
        MessageBoxButtons.OK, MessageBoxIcon.Warning);
        txtTotalPaid.Focus();
        return;
    }
    double val1 = 0;
    double val2 = 0;
    double.TryParse(txtGrandTotal.Text, out val1);
    double.TryParse(txtTotalPaid.Text, out val2);
    if (val2 > val1)
    {
        MessageBox.Show("O total não pode ser maior do que o valor pago", "Erro", MessageBoxButtons.OK, MessageBoxIcon.Error);
        txtTotalPaid.Text = "";
        txtTotalPaid.Focus();
        return;

    }
    cc.con = new SqlConnection(cs.DBConn);
    cc.con.Open();
    string ct = "SELECT * FROM CustomerMembership WHERE DateFrom <= '" + dtpDateTo.Value.Date + "' AND DateTo >= '" + dtpDateFrom.Value.Date + "' and CustomerID=" + txtM_ID.Text + "";
    cc.cmd = new SqlCommand(ct);
    cc.cmd.Connection = cc.con;
    cc.rdr = cc.cmd.ExecuteReader();
    if (cc.rdr.Read())
    {
        MessageBox.Show("A mensalidade ainda não expirou.." + "\n" + "O pagamento não é permitido", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        if ((cc.rdr != null))
        {
            cc.rdr.Close();
        }
        return;
    }
    cc.con = new SqlConnection(cs.DBConn);
    cc.con.Open();
    string cb = "insert into CustomerMembership(CM_ID,BillDate,CustomerID,MembershipID,DateFrom,Months,DateTo,ChargesPerMonth,TotalCharges,DiscountPer,DiscountAmount,SubTotal,VATPer,VATAmount,ServiceTaxPer,ServiceTaxAmount,GrandTotal,TotalPaid) VALUES (@d1,@d2,@d3,@d4,@d5,@d6,@d7,@d8,@d9,@d10,@d11,@d12,@d13,@d14,@d15,@d16,@d17,@d18)";
    cc.cmd = new SqlCommand(cb);
    cc.cmd.Connection = cc.con;
    cc.cmd.Parameters.AddWithValue("@d1",txtMembershipID.Text);
    cc.cmd.Parameters.AddWithValue("@d2",dtpBillDate.Value);
    cc.cmd.Parameters.AddWithValue("@d3",txtM_ID.Text);
    cc.cmd.Parameters.AddWithValue("@d4", txtMembershipTypeID.Text);
    cc.cmd.Parameters.AddWithValue("@d5", dtpDateFrom.Value);
    cc.cmd.Parameters.AddWithValue("@d6", txtMonths.Text);
    cc.cmd.Parameters.AddWithValue("@d7", dtpDateTo.Value);
    cc.cmd.Parameters.AddWithValue("@d8", txtChargesPerMonth.Text);
    cc.cmd.Parameters.AddWithValue("@d9", txtTotalCharges.Text);
    cc.cmd.Parameters.AddWithValue("@d10",txtDiscountPer.Text);
    cc.cmd.Parameters.AddWithValue("@d11",txtDiscountAmount.Text);
    cc.cmd.Parameters.AddWithValue("@d12",txtSubTotal.Text);
    cc.cmd.Parameters.AddWithValue("@d13", txtVATPer.Text);
    cc.cmd.Parameters.AddWithValue("@d14", txtVATAmount.Text);
    cc.cmd.Parameters.AddWithValue("@d15", txtServiceTaxPer.Text);
    cc.cmd.Parameters.AddWithValue("@d16", txtServiceTaxAmount.Text);
    cc.cmd.Parameters.AddWithValue("@d17", txtGrandTotal.Text);
    cc.cmd.Parameters.AddWithValue("@d18", txtTotalPaid.Text);
    cc.cmd.ExecuteReader();
    cc.con.Close();
    st1 = lblUser.Text;
    st2 = "Foi adicionada uma nova mensalidade com o id '" + txtMembershipID.Text + "' ao membro '" + txtMemberName.Text + "'";
    cf.LogFunc(st1, System.DateTime.Now, st2);
    btnSave.Enabled = false;
    MessageBox.Show("Gravado com sucesso", "Registo", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message, "Erro", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

Sql table:

CREATE TABLE [dbo].[CustomerMembership] (
    [CM_ID]            INT            NOT NULL,
    [CustomerID]       INT             NOT NULL,
    [MembershipID]     INT             NOT NULL,
    [DateFrom]         DATETIME        NOT NULL,
    [Months]           VARCHAR (2)     NOT NULL,
    [DateTo]           DATETIME        NOT NULL,
    [ChargesPerMonth]  DECIMAL (18, 2) NOT NULL,
    [DiscountPer]      DECIMAL (3)     NOT NULL,
    [VATPer]           DECIMAL (3)     NOT NULL,
    [VATAmount]        DECIMAL (3)     NOT NULL,
    [ServiceTaxPer]    DECIMAL (3)     NOT NULL,
    [ServiceTaxAmount] DECIMAL (3)     NOT NULL,
    [TotalCharges]     DECIMAL (18, 2) NOT NULL,
    [BillDate]         DATETIME        NOT NULL,
    [SubTotal]         DECIMAL (18, 2) NOT NULL,
    [GrandTotal]       DECIMAL (18, 2) NOT NULL,
    [TotalPaid]        DECIMAL (18, 2) NOT NULL,
    [DiscountAmount]   DECIMAL (3)     NOT NULL,
    CONSTRAINT [PK_CustomerMembership] PRIMARY KEY CLUSTERED ([CM_ID] ASC),
    CONSTRAINT [FK_CustomerMembership_Customer] FOREIGN KEY ([CustomerID]) REFERENCES [dbo].[Customer] ([C_ID]) ON UPDATE CASCADE,
    CONSTRAINT [FK_CustomerMembership_Membership] FOREIGN KEY ([MembershipID]) REFERENCES [dbo].[Membership] ([M_ID]) ON UPDATE CASCADE
);

What I have tried:

Tryied to set the CM_ID to VARCHAR and then program a sort of algorithm to set the id to I-{number} instead of just {number}.
Tryied to set the Values according to the Add function
Ex:
...Add("@d1", SqlDbType.Int).Value = txtMemberShipID.Text;
But this didn't work too.

Any ideias?