First Add...
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@CompanyID",CompanyID);
May be you have forget to Declare @companyID
And Make sure You are dealing with SP like...
Stored Procedure
CREATE dbo.mySP
@companyID INT,
@companyName NVARCHAR
<
AS
BEGIN
INSERT INTO TBL VALUES(@companyID,@companyName)
END
Hope This Help
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Pratik Bhuva