intput string not in correct format...when converting a string to datetime...error?

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C#

I am trying to pass a parameter to a sql select query.

for some reason, no matter what i try, i keep getting the same error:
input string not in the corect format

and the suggestion:
when converting a string to datetime, parse the string to take the date before putting each variable into the datetime object.

i'm stumped as to what to do. here's the code.

sql query:

ALTER PROCEDURE SearchAllPlayers
(
@personName,
@personPay,
@IDs
)
 
SELECT DISTINCT
                         person.personID, sports.sportsID, person.personName, person.personPay, sports.sport,
 
FROM            sports INNER JOIN
                person INNER JOIN
                personSport ON personSport.personID = person.personID
                       INNER JOIN
                personSport ON personSport.sportID = sports.sportsID
 
WHERE        (person.personName LIKE '%' + @personName + '%')
              AND
             (person.personPay >= @personPay OR 0 = @personPay)
              AND
             (person.regDate >= { fn CURDATE() }
              AND
             (sports.sportID IN
                    (SELECT   ID FROM dbo.fnSplitter(@IDs) AS fnSplitter_1) OR @IDs = 0)

protected void Button1_Click(object sender, EventArgs e)
    {
        searchGrid();
    }
 
    protected void searchGrid()
    {
        SqlConnection conn = new SqlConnection(connSTR);
        com = new SqlCommand();
        conn.Open();
 
        com.Connection = conn;
 
        com.CommandText = "SearchAllPlayers";
        com.CommandType = CommandType.StoredProcedure;
 
        string StringWithDelimiter = string.Empty;
        for (int i = 0; i < DropDownCheckBoxes1.Items.Count; i++)
        {
            if (DropDownCheckBoxes1.Items[i].Selected)
                StringWithDelimiter += DropDownCheckBoxes1.Items[i].Value + ";";
        }
        
        com.Parameters.Add("@personName", SqlDbType.VarChar).Value = personName.Text;

        //next line is where I am having problems
        com.Parameters.Add("@personPay", SqlDbType.Decimal).Value = ??????
        com.Parameters.Add("@IDs", SqlDbType.VarChar).Value = StringWithDelimiter;
 
        sqlDa = new SqlDataAdapter(com);
        dS = new DataSet();
        sqlDa.Fill(dS);
 
        conn.Close();
        GridView1.DataSource = dS;
        GridView1.DataBind();
 
    }

so far i've tried the following combinations, all to know avail.

com.parameters.add("@playerPay", sqldbtype.decimal).value = playerPayTextBox.Text;
this doesn't seem to work, i get the following error:
"Error converting data type nvarchar to decimal."

so then i tried this:
com.parameters.add("@playerPay", sqldbtype.decimal).value = playerPayTextBox.tostring();
i get the same error:
"Error converting data type nvarchar to decimal."

which makes sense, so then i tried:
com.parameters.add("@playerPay", sqldbtype.decimal).value = decimal.parse(playerPayTextBox.tostring());
error: "Input string was not in a correct format." - then the datetime thing...

com.parameters.add("@playerPay", sqldbtype.decimal).value = decimal.parse(playerPayTextBox.text);
error: "Input string was not in a correct format." - then the datetime thing...

com.parameters.add("@playerPay", sqldbtype.decimal).value = convert.todecimal(playerPayTextBox.text);
error: "Input string was not in a correct format." - then the datetime thing...

com.parameters.add("@playerPay", sqldbtype.decimal).value = convert.todecimal(playerPayTextBox.text);
error: "Input string was not in a correct format." - then the datetime thing...

not sure what to do